Protected Engine.stop() from recursive calls from different threads

darcs-hash:20090713190407-58103-59af8e851d44545ec8c5e31a119fbf8b069c4c29
Added PJSIP patch to ignore missing rtpmap for dynamic pt in incoming SDP

darcs-hash:20090714141138-58103-2acbe82a528a88c5fc29355a909fe299c69cded1