Fix for event name in sip_subscribe_winfo.py

darcs-hash:20090526080427-58103-e530ef1613c2d3ce8281668f2e8f2d624db92ab0
Minor fixes for extra_headers in Subscription object

darcs-hash:20090526082732-58103-47a2251926de55980c8f929c0ff3f51d1fb59fd1