Added '?' key command to display control keys in sip_register

darcs-hash:20090216124059-1e3d8-a579136f2dc9ee4fe2e6359f327869a542f5e261
Added '?' key command to display control keys in sip_subscribe_presence

darcs-hash:20090216124603-1e3d8-ddff92572c652166455b40520952397612bd8f44