Added subtring-based account selection to sip_subscribe_xcap_diff

Ignore-this: 72af915b5ea778727092a5b7b22b3d5f

darcs-hash:20090521072802-1e3d8-46ac8a5ed647cc1e4d32c30771ca1b559c90e61b
Added substring-based account_selection to xcap_rls_services

Ignore-this: 2315b69e97a50fa1c4fe55167efe6da6

darcs-hash:20090521072826-1e3d8-e5ce77e82c262fc772a462cfb2af0ec5131289d9