Added body to xcap-diff subscribe in sip_subscribe_xcap_diff

Ignore-this: 78c19ea5a43d813edcd39c383935c48

darcs-hash:20090526092736-1e3d8-3d5be719a1ac8ff9c1aa13ba3bf7c0ff7516780a
Fix for extra_headers in Subscription while ending

darcs-hash:20090526093420-58103-7b89d3fc09303aaeb97a189847fc7042c6b1131c