Added command to sip_publish_presence to toggle SIP tracing on console

darcs-hash:20090214012253-1e3d8-7611b44188231413e7346c21be2115b70e9978d6
Added command to sip_subscribe_presence to toggle SIP tracing on console

darcs-hash:20090214012417-1e3d8-18b6f461e5593971641324537059a9313780e49b