Fixed #1764: Use latest early media SDP received on forked early media on 18x response



git-svn-id: http://svn.pjsip.org/repos/pjproject@4830 74dad513-b988-da41-8d7b-12977e46ad98
Re #1764: Add reference to ticket number



git-svn-id: http://svn.pjsip.org/repos/pjproject@4831 74dad513-b988-da41-8d7b-12977e46ad98