fixed shutdown functions not to silent pypjua errors

Ignore-this: 2a7b20fce36d647aa7433dafaa68d4b6
* removed IncomingHandler.wait_and_handle function
* renamed ChatSession.shutdown to end
* changed sip_im_session's accepting behaviour: it will issue ringing immediatelly for each new incoming connection (it used to wait for the user to accept or reject one connection before issuing ringing to the following one)

darcs-hash:20090202114858-b2873-581fe9a0e76b88e4e7631c37ae744dce1463b259