app_chanspy: Documentation Update To Clarify "x" Option

When using the "x" option (specify a DTMF digit to exit the application), it is
not obvious in the documentation that this only works when spying on a channel.
If a channel being used to spy on other channels is waiting to connect to a
channel or is no longer attached to a channel, the DTMF is ignored.

As noted on the issue tracker, since there are workarounds available and this is
a rarely used option we are opting for a documentation change here.

(closes issue ASTERISK-22661)
Reported by: Chris Hillman
Patches:
    asterisk-22661-doc-clarify-chan_spy.diff
                                     uploaded by Michael L. Young (license 5026)

Review: https://reviewboard.asterisk.org/r/2990/


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@408536 65c4cc65-6c06-0410-ace0-fbb531ad65f3

apps/app_chanspy.c

@@ -158,7 +158,9 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 					</option>
 					<option name="x">
 						<argument name="digit" required="true">
-							<para>Specify a DTMF digit that can be used to exit the application.</para>
+							<para>Specify a DTMF digit that can be used to exit the application while actively
+							spying on a channel. If there is no channel being spied on, the DTMF digit will be
+							ignored.</para>
 						</argument>
 					</option>
 					<option name="X">
@@ -295,7 +297,9 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 					</option>
 					<option name="x">
 						<argument name="digit" required="true">
-							<para>Specify a DTMF digit that can be used to exit the application.</para>
+							<para>Specify a DTMF digit that can be used to exit the application while actively
+							spying on a channel. If there is no channel being spied on, the DTMF digit will be
+							ignored.</para>
 						</argument>
 					</option>
 					<option name="X">