Fix application references to Background

The app is actually named "BackGround" but several references
in XML documentation were spelled "Background" with the lower
case "g".  This was causing documentation links to return
"not found" messages.

(cherry picked from commit 48acf00eab)

apps/app_playback.c

@@ -94,7 +94,7 @@
 			<para>WaitExten (application) -- wait for digits from caller, optionally play music on hold</para>
 		</description>
 		<see-also>
-			<ref type="application">Background</ref>
+			<ref type="application">BackGround</ref>
 			<ref type="application">WaitExten</ref>
 			<ref type="application">ControlPlayback</ref>
 			<ref type="agi">stream file</ref>

main/pbx_builtins.c

@@ -435,7 +435,7 @@
 			of the given <replaceable>string</replaceable>. If the channel variable
 			<variable>SAY_DTMF_INTERRUPT</variable> is set to 'true' (case insensitive),
 			then this application will react to DTMF in the	same way as
-			<literal>Background</literal>.</para>
+			<literal>BackGround</literal>.</para>
 		</description>
 		<see-also>
 			<ref type="application">SayDigits</ref>
@@ -479,7 +479,7 @@
 			given <replaceable>string</replaceable>.  Optionally, a <replaceable>casetype</replaceable> may be
 			specified.  This will be used for case-insensitive or case-sensitive pronunciations. If the channel
 			variable <variable>SAY_DTMF_INTERRUPT</variable> is set to 'true' (case insensitive), then this
-			application will react to DTMF in the same way as <literal>Background</literal>.</para>
+			application will react to DTMF in the same way as <literal>BackGround</literal>.</para>
 		</description>
 		<see-also>
 			<ref type="application">SayDigits</ref>
@@ -503,7 +503,7 @@
 			the given number. This will use the language that is currently set for the channel.
 			If the channel variable <variable>SAY_DTMF_INTERRUPT</variable> is set to 'true'
 			(case insensitive), then this application will react to DTMF in the same way as
-			<literal>Background</literal>.</para>
+			<literal>BackGround</literal>.</para>
 		</description>
 		<see-also>
 			<ref type="application">SayAlpha</ref>
@@ -527,7 +527,7 @@
 			in the current language. Currently only English and US Dollars is supported.
 			If the channel variable <variable>SAY_DTMF_INTERRUPT</variable> is set to 'true'
 			(case insensitive), then this application will react to DTMF in the same way as
-			<literal>Background</literal>.</para>
+			<literal>BackGround</literal>.</para>
 		</description>
 		<see-also>
 			<ref type="application">SayAlpha</ref>
@@ -552,7 +552,7 @@
 			specified. This will use the language that is currently set for the channel. See the CHANNEL()
 			function for more information on setting the language for the channel. If the channel variable
 			<variable>SAY_DTMF_INTERRUPT</variable> is set to 'true' (case insensitive), then this
-			application will react to DTMF in the same way as <literal>Background</literal>.</para>
+			application will react to DTMF in the same way as <literal>BackGround</literal>.</para>
 		</description>
 		<see-also>
 			<ref type="application">SayAlpha</ref>
@@ -578,7 +578,7 @@
 			specified. This will use the language that is currently set for the channel. See the CHANNEL()
 			function for more information on setting the language for the channel. If the channel variable
 			<variable>SAY_DTMF_INTERRUPT</variable> is set to 'true' (case insensitive), then this
-			application will react to DTMF in the same way as <literal>Background</literal>.</para>
+			application will react to DTMF in the same way as <literal>BackGround</literal>.</para>
 		</description>
 		<see-also>
 			<ref type="application">SayAlpha</ref>
@@ -601,7 +601,7 @@
 			<para>This application will play the sounds from the phonetic alphabet that correspond to the
 			letters in the given <replaceable>string</replaceable>. If the channel variable
 			<variable>SAY_DTMF_INTERRUPT</variable> is set to 'true' (case insensitive), then this
-			application will react to DTMF in the same way as <literal>Background</literal>.</para>
+			application will react to DTMF in the same way as <literal>BackGround</literal>.</para>
 		</description>
 		<see-also>
 			<ref type="application">SayAlpha</ref>
@@ -692,7 +692,7 @@
 			of <replaceable>seconds</replaceable>.</para>
 		</description>
 		<see-also>
-			<ref type="application">Background</ref>
+			<ref type="application">BackGround</ref>
 			<ref type="function">TIMEOUT</ref>
 		</see-also>
 	</application>