chan_sip: Add MESSAGE request to allowed methods

The allowed methods advertised by chan_sip did not previously note the MESSAGE
request. Even in Asterisk 1.8, we do accept in-dialog MESSAGE requests; we
should advertise that we support MESSAGE requests.

ASTERISK-23504 #close
ASTERISK-23504 #comment Reported by: Martin Kontsek
ASTERISK-23504 #comment Patch sip.h_patch.diff uploaded by Martin Kontsek (license 6587)

Review: https://reviewboard.asterisk.org/r/3396/
........

Merged revisions 411372 from http://svn.asterisk.org/svn/asterisk/branches/1.8


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/11@411373 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/sip/include/sip.h

@@ -161,7 +161,7 @@
  *  \todo This string should be set dynamically. We only support REFER and SUBSCRIBE if we have
  *  allowsubscribe and allowrefer on in sip.conf.
  */
-#define ALLOWED_METHODS "INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY, INFO, PUBLISH"
+#define ALLOWED_METHODS "INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY, INFO, PUBLISH, MESSAGE"
 
 /*! \brief Standard SIP unsecure port for UDP and TCP from RFC 3261. DO NOT CHANGE THIS */
 #define STANDARD_SIP_PORT	5060