An account can now override {{{handleOfflineAsStatusChange}}} to be told about offlin...

An account can now override {{{handleOfflineAsStatusChange}}} to be told about offline status changes as with other statuses. This should probably be something all accounts just do, rather than treating offline as a special case of status, but this lets us hook into the gadu-gadu offline status messages without widespread changes to other account types (which would be unacceptable at this stage of the 1.0 game)

git-svn-id: svn://svn.adiumx.com/adium/trunk@17725 1c916fce-81e2-0310-a464-8ca513f45935