sip_im_session2: change formatting of the prompt to include port when it's not default

darcs-hash:20090316144234-b2873-d1720df3a437baddd814b8595a876db2526ae40d
sip_im_session2: don't print traceback for SessionError

darcs-hash:20090316144317-b2873-aec33ed7d9c4022dca4e115d51911268d563c001