Update config to note only U.S. tones supported at this time (bug #280)

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@1520 65c4cc65-6c06-0410-ace0-fbb531ad65f3

configs/zapata.conf.sample

@@ -199,7 +199,9 @@ immediate=no
 ; progress attempts to determine answer, busy, and ringing on phone lines.
 ; This feature is HIGHLY EXPERIMENTAL and can easily detect false answers,
 ; so don't count on it being very accurate.  Also, it is ONLY configured for
-; standard U.S. tones 
+; standard U.S. tones.  This feature can also easily detect false hangups.
+; The symptoms of this is being disconnected in the middle of a call for no
+; reason.
 ;
 ;callprogress=yes
 ;