Re #1784: Revert API change



git-svn-id: http://svn.pjsip.org/repos/pjproject@4919 74dad513-b988-da41-8d7b-12977e46ad98
Fixed #1785: Add support for sending initial INVITE/re-INVITE/UPDATE without SDP



git-svn-id: http://svn.pjsip.org/repos/pjproject@4920 74dad513-b988-da41-8d7b-12977e46ad98