Added command to sip_register to toggle SIP tracing on console

darcs-hash:20090214003203-1e3d8-f0bf64797e50caaabe8f717c3ed8c4d5da4a7289
Added command to sip_audio_session to toggle SIP tracing on console

darcs-hash:20090214011826-1e3d8-f3c5c0f99472f3a886abe5f7ff7b7dd5667a46ad