Added PJSIP patch to terminate re-INVITE transaction on CANCEL

As usual, do "python setup.py build_ext --pjsip-clean-compile" after
pulling this patch.

darcs-hash:20090505184000-58103-d216fc0bb44a1685757919e38c872ece2e193d4a
Added new RFC number for former draft

darcs-hash:20090506090812-58252-a4b22d901d70911d27c5055bfe6f529560c6f4b2