fix sip_im_session to ignore path in incoming file transfers

darcs-hash:20090205090435-b2873-31a5bb2c9a28d1f67c9f2b7a1bdca83f3a9e289b
fix sip_im_session to send Ringing in case of incoming file transfer

darcs-hash:20090205090515-b2873-7089d0f3c26a671f5e86cbb60e2ae6bcb720c6b3