Fix stuck DTMF when bridge is broken.

When a bridge is broken by an AMI Redirect action or the ChannelRedirect
application, an in progress DTMF digit could be stuck sending forever.

* Made simulate a DTMF end event when a bridge is broken and a DTMF digit
was in progress.

(closes issue ASTERISK-20492)
Reported by: Jeremiah Gowdy
Patches:
      bridge_end_dtmf-v3.patch.txt (license #6358) patch uploaded by Jeremiah Gowdy
      Modified to jira_asterisk_20492_v1.8.patch
      jira_asterisk_20492_v1.8.patch (license #5621) patch uploaded by rmudgett
Tested by: rmudgett

Review: https://reviewboard.asterisk.org/r/2169/
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Merged revisions 375964 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 375965 from http://svn.asterisk.org/svn/asterisk/branches/10
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Merged revisions 375966 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@375967 65c4cc65-6c06-0410-ace0-fbb531ad65f3

include/asterisk/features.h

@@ -169,6 +169,18 @@ int ast_parking_ext_valid(const char *exten_str, struct ast_channel *chan, const
 /*! \brief Determine system call pickup extension */
 const char *ast_pickup_ext(void);
 
+/*!
+ * \brief Simulate a DTMF end on a broken bridge channel.
+ *
+ * \param chan Channel sending DTMF that has not ended.
+ * \param digit DTMF digit to stop.
+ * \param start DTMF digit start time.
+ * \param why Reason bridge broken.
+ *
+ * \return Nothing
+ */
+void ast_bridge_end_dtmf(struct ast_channel *chan, char digit, struct timeval start, const char *why);
+
 /*! \brief Bridge a call, optionally allowing redirection */
 int ast_bridge_call(struct ast_channel *chan, struct ast_channel *peer,struct ast_bridge_config *config);