Modify comments in MeetMe application documentation about DAHDI.

The MeetMe application documentation has some comments about usage of DAHDI,
and they were a bit outdated relative to modern DAHDI releases. This patch
changes the comment to just tell the user that a functional DAHDI timing
source is required, and no longer mention 'dahdi_dummy', since that module
does not exist in current DAHDI releases.
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Merged revisions 342990 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 342991 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@342992 65c4cc65-6c06-0410-ace0-fbb531ad65f3

apps/app_meetme.c

@@ -233,7 +233,7 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 			<para>Enters the user into a specified MeetMe conference.  If the <replaceable>confno</replaceable>
 			is omitted, the user will be prompted to enter one.  User can exit the conference by hangup, or
 			if the <literal>p</literal> option is specified, by pressing <literal>#</literal>.</para>
-			<note><para>The DAHDI kernel modules and at least one hardware driver (or dahdi_dummy)
+			<note><para>The DAHDI kernel modules and a functional DAHDI timing source (see dahdi_test)
 			must be present for conferencing to operate properly. In addition, the chan_dahdi channel driver
 			must be loaded for the <literal>i</literal> and <literal>r</literal> options to operate at
 			all.</para></note>