sip_session: mention [audio|chat] command line argument in the description

darcs-hash:20090330093351-b2873-cc3457e33204f113b49e225631f878cb2128d7ca
sip_session: remove ABCD from virtual numpad

darcs-hash:20090330093455-b2873-b014251ca253357773ddb912ec8b1b41b144d41f