Merging the issue11259 branch.

The purpose of this branch was to take into account
"burps" which could cause jitterbuffers to misbehave.
One such example is if the L option to Dial() were used
to inject audio into a bridged conversation at regular
intervals. Since the audio here was not passed through
the jitterbuffer, it would cause a gap in the jitterbuffer's
timestamps which would cause a frames to be dropped for a 
brief period.

Now ast_generic_bridge will empty and reset the jitterbuffer
each time it is called. This causes injected audio to be handled
properly.

ast_generic_bridge also will empty and reset the jitterbuffer
if it receives an AST_CONTROL_SRCUPDATE frame since the change
in audio source could negatively affect the jitterbuffer.

All of this was made possible by adding a new public API call
to the abstract_jb called ast_jb_empty_and_reset.

(closes issue #11259)
Reported by: plack
Tested by: putnopvut



git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@135841 65c4cc65-6c06-0410-ace0-fbb531ad65f3

include/asterisk/abstract_jb.h

@@ -212,6 +212,12 @@ void ast_jb_configure(struct ast_channel *chan, const struct ast_jb_conf *conf);
  */
 void ast_jb_get_config(const struct ast_channel *chan, struct ast_jb_conf *conf);
 
+/*!
+ * \brief drops all frames from a jitterbuffer and resets it
+ * \param c0 one channel of a bridge
+ * \param c1 the other channel of the bridge
+ */
+void ast_jb_empty_and_reset(struct ast_channel *c0, struct ast_channel *c1);
 
 #if defined(__cplusplus) || defined(c_plusplus)
 }