sip_session2: remove unused import

darcs-hash:20090422105759-b2873-6cf94dff0f212f90753e09f6fd8d3a77ce02667b
sip_session2: split :call command into :audio and :chat

darcs-hash:20090422105817-b2873-2838f8d313bf126243624f7aec1e0ff1ed2daa28