Add the ability to retrieve the source port of a SIP call.

This adds the ability to call CHANNEL(recvport) on chan_sip
channels to see the port on which an INVITE was received.

ASTERISK-24040 #close
Reported by dtryba
Patches:
	dialplan_functions.patch uploaded by dtryba (License #6628)

Review: https://reviewboard.asterisk.org/r/3781



git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@419970 f38db490-d61c-443f-a65b-d21fe96a405b
Remove duplicate definitions of ast_format_vp8.

git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@420007 f38db490-d61c-443f-a65b-d21fe96a405b