docs: Add version information to AGI command XML elements.

This process was a bit different than the others because everything
is in the same file, there's an array that contains the command
names and their handler functions, and the last command was created
over 15 years ago.

* Dump a `git blame` of res/res_agi.c from BEFORE the handle_* prototypes
  were changed.
* Create a command <> handler function xref by parsing the the agi_command
  array.
* For each entry, grep the function definition line "static int handle_*"
  from the git blame output and capture the commit.  This will be the
  commit the command was created in.
* Do a `git tag --contains <commit> | sort -V | head -1` to get the
  tag the function was created in.
* Add a single since/version element to the command XML.  Multiple versions
  aren't supported here because the branching and tagging scheme changed
  several times in the 2000's.

res/res_agi.c

@@ -73,6 +73,9 @@
 
 /*** DOCUMENTATION
 	<agi name="answer" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Answer channel
 		</synopsis>
@@ -87,6 +90,9 @@
 		</see-also>
 	</agi>
 	<agi name="asyncagi break" language="en_US">
+		<since>
+			<version>1.8.0</version>
+		</since>
 		<synopsis>
 			Interrupts Async AGI
 		</synopsis>
@@ -101,6 +107,9 @@
 		</see-also>
 	</agi>
 	<agi name="channel status" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Returns status of the connected channel.
 		</synopsis>
@@ -143,6 +152,9 @@
 		</see-also>
 	</agi>
 	<agi name="control stream file" language="en_US">
+		<since>
+			<version>1.2.0</version>
+		</since>
 		<synopsis>
 			Sends audio file on channel and allows the listener to control the stream.
 		</synopsis>
@@ -198,6 +210,9 @@
 		</see-also>
 	</agi>
 	<agi name="database del" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Removes database key/value
 		</synopsis>
@@ -219,6 +234,9 @@
 		</see-also>
 	</agi>
 	<agi name="database deltree" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Removes database keytree/value
 		</synopsis>
@@ -239,6 +257,9 @@
 		</see-also>
 	</agi>
 	<agi name="database get" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Gets database value
 		</synopsis>
@@ -262,6 +283,9 @@
 		</see-also>
 	</agi>
 	<agi name="database put" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Adds/updates database value
 		</synopsis>
@@ -284,6 +308,9 @@
 		</see-also>
 	</agi>
 	<agi name="exec" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Executes a given Application
 		</synopsis>
@@ -305,6 +332,9 @@
 		</see-also>
 	</agi>
 	<agi name="get data" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Prompts for DTMF on a channel
 		</synopsis>
@@ -322,6 +352,9 @@
 		</see-also>
 	</agi>
 	<agi name="get full variable" language="en_US">
+		<since>
+			<version>1.2.0</version>
+		</since>
 		<synopsis>
 			Evaluates a channel expression
 		</synopsis>
@@ -349,6 +382,9 @@
 		</see-also>
 	</agi>
 	<agi name="get option" language="en_US">
+		<since>
+			<version>1.2.0</version>
+		</since>
 		<synopsis>
 			Stream file, prompt for DTMF, with timeout.
 		</synopsis>
@@ -367,6 +403,9 @@
 		</see-also>
 	</agi>
 	<agi name="get variable" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Gets a channel variable.
 		</synopsis>
@@ -386,6 +425,9 @@
 		</see-also>
 	</agi>
 	<agi name="hangup" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Hangup a channel.
 		</synopsis>
@@ -401,6 +443,9 @@
 		</see-also>
 	</agi>
 	<agi name="noop" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Does nothing.
 		</synopsis>
@@ -413,6 +458,9 @@
 		</see-also>
 	</agi>
 	<agi name="receive char" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Receives one character from channels supporting it.
 		</synopsis>
@@ -434,6 +482,9 @@
 		</see-also>
 	</agi>
 	<agi name="receive text" language="en_US">
+		<since>
+			<version>1.2.0</version>
+		</since>
 		<synopsis>
 			Receives text from channels supporting it.
 		</synopsis>
@@ -455,6 +506,9 @@
 		</see-also>
 	</agi>
 	<agi name="record file" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Records to a given file.
 		</synopsis>
@@ -506,6 +560,9 @@
 		</see-also>
 	</agi>
 	<agi name="say alpha" language="en_US">
+		<since>
+			<version>1.2.0</version>
+		</since>
 		<synopsis>
 			Says a given character string.
 		</synopsis>
@@ -530,6 +587,9 @@
 		</see-also>
 	</agi>
 	<agi name="say digits" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Says a given digit string.
 		</synopsis>
@@ -554,6 +614,9 @@
 		</see-also>
 	</agi>
 	<agi name="say number" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Says a given number.
 		</synopsis>
@@ -579,6 +642,9 @@
 		</see-also>
 	</agi>
 	<agi name="say phonetic" language="en_US">
+		<since>
+			<version>1.0.0</version>
+		</since>
 		<synopsis>
 			Says a given character string with phonetics.
 		</synopsis>
@@ -603,6 +669,9 @@
 		</see-also>
 	</agi>
 	<agi name="say date" language="en_US">
+		<since>
+			<version>1.2.0</version>
+		</since>
 		<synopsis>
 			Says a given date.
 		</synopsis>
@@ -630,6 +699,9 @@
 		</see-also>
 	</agi>
 	<agi name="say time" language="en_US">
+		<since>
+			<version>1.0.0</version>
+		</since>
 		<synopsis>
 			Says a given time.
 		</synopsis>
@@ -657,6 +729,9 @@
 		</see-also>
 	</agi>
 	<agi name="say datetime" language="en_US">
+		<since>
+			<version>1.2.0</version>
+		</since>
 		<synopsis>
 			Says a given time as specified by the format given.
 		</synopsis>
@@ -693,6 +768,9 @@
 		</see-also>
 	</agi>
 	<agi name="send image" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Sends images to channels supporting it.
 		</synopsis>
@@ -710,6 +788,9 @@
 		</see-also>
 	</agi>
 	<agi name="send text" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Sends text to channels supporting it.
 		</synopsis>
@@ -731,6 +812,9 @@
 		</see-also>
 	</agi>
 	<agi name="set autohangup" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Autohangup channel in some time.
 		</synopsis>
@@ -747,6 +831,9 @@
 		</see-also>
 	</agi>
 	<agi name="set callerid" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Sets callerid for the current channel.
 		</synopsis>
@@ -761,6 +848,9 @@
 		</see-also>
 	</agi>
 	<agi name="set context" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Sets channel context.
 		</synopsis>
@@ -777,6 +867,9 @@
 		</see-also>
 	</agi>
 	<agi name="set extension" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Changes channel extension.
 		</synopsis>
@@ -793,6 +886,9 @@
 		</see-also>
 	</agi>
 	<agi name="set music" language="en_US">
+		<since>
+			<version>0.5.0</version>
+		</since>
 		<synopsis>
 			Enable/Disable Music on hold generator
 		</synopsis>
@@ -816,6 +912,9 @@
 		</see-also>
 	</agi>
 	<agi name="set priority" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Set channel dialplan priority.
 		</synopsis>
@@ -833,6 +932,9 @@
 		</see-also>
 	</agi>
 	<agi name="set variable" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Sets a channel variable.
 		</synopsis>
@@ -850,6 +952,9 @@
 		</see-also>
 	</agi>
 	<agi name="stream file" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Sends audio file on channel.
 		</synopsis>
@@ -890,6 +995,9 @@
 		</see-also>
 	</agi>
 	<agi name="tdd mode" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Toggles TDD mode (for the deaf).
 		</synopsis>
@@ -910,6 +1018,9 @@
 		</see-also>
 	</agi>
 	<agi name="verbose" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Logs a message to the asterisk verbose log.
 		</synopsis>
@@ -927,6 +1038,9 @@
 		</see-also>
 	</agi>
 	<agi name="wait for digit" language="en_US">
+		<since>
+			<version>0.4.0</version>
+		</since>
 		<synopsis>
 			Waits for a digit to be pressed.
 		</synopsis>
@@ -945,6 +1059,9 @@
 		</see-also>
 	</agi>
 	<agi name="speech create" language="en_US">
+		<since>
+			<version>1.6.0</version>
+		</since>
 		<synopsis>
 			Creates a speech object.
 		</synopsis>
@@ -966,6 +1083,9 @@
 		</see-also>
 	</agi>
 	<agi name="speech set" language="en_US">
+		<since>
+			<version>1.6.0</version>
+		</since>
 		<synopsis>
 			Sets a speech engine setting.
 		</synopsis>
@@ -988,6 +1108,9 @@
 		</see-also>
 	</agi>
 	<agi name="speech destroy" language="en_US">
+		<since>
+			<version>1.6.0</version>
+		</since>
 		<synopsis>
 			Destroys a speech object.
 		</synopsis>
@@ -1008,6 +1131,9 @@
 		</see-also>
 	</agi>
 	<agi name="speech load grammar" language="en_US">
+		<since>
+			<version>1.6.0</version>
+		</since>
 		<synopsis>
 			Loads a grammar.
 		</synopsis>
@@ -1030,6 +1156,9 @@
 		</see-also>
 	</agi>
 	<agi name="speech unload grammar" language="en_US">
+		<since>
+			<version>1.6.0</version>
+		</since>
 		<synopsis>
 			Unloads a grammar.
 		</synopsis>
@@ -1051,6 +1180,9 @@
 		</see-also>
 	</agi>
 	<agi name="speech activate grammar" language="en_US">
+		<since>
+			<version>1.6.0</version>
+		</since>
 		<synopsis>
 			Activates a grammar.
 		</synopsis>
@@ -1072,6 +1204,9 @@
 		</see-also>
 	</agi>
 	<agi name="speech deactivate grammar" language="en_US">
+		<since>
+			<version>1.6.0</version>
+		</since>
 		<synopsis>
 			Deactivates a grammar.
 		</synopsis>
@@ -1093,6 +1228,9 @@
 		</see-also>
 	</agi>
 	<agi name="speech recognize" language="en_US">
+		<since>
+			<version>1.6.0</version>
+		</since>
 		<synopsis>
 			Recognizes speech.
 		</synopsis>