Update AMI Getvar and Setvar documentation about supplying a channel name.

(closes issue ASTERISK-18958)
Reported by: Red
Patches:
      jira_asterisk_18958_v1.8.patch (license #5621) patch uploaded by rmudgett
........

Merged revisions 347438 from http://svn.asterisk.org/svn/asterisk/branches/1.8


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/10@347439 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/manager.c

@@ -220,6 +220,9 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 		</syntax>
 		<description>
 			<para>Set a global or local channel variable.</para>
+			<note>
+				<para>If a channel name is not provided then the variable is global.</para>
+			</note>
 		</description>
 	</manager>
 	<manager name="Getvar" language="en_US">
@@ -237,6 +240,9 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 		</syntax>
 		<description>
 			<para>Get the value of a global or local channel variable.</para>
+			<note>
+				<para>If a channel name is not provided then the variable is global.</para>
+			</note>
 		</description>
 	</manager>
 	<manager name="GetConfig" language="en_US">