API:

API:
* Added ApiQueryBase::addJoin() which provides a cleaner interface to construct JOIN queries. Behind the scenes this still uses the old, ugly way, but it'll be easy to rewrite when/if the Database class gets its own function for JOINs
* Used addJoin() in query modules where necessary
* Removed FORCE INDEX (rc_timestamp) from ApiQueryRecentchanges: it's nigh impossible to integrate with addJoin() and it doesn't seem to be necessary anyway (my MySQL instance automatically chooses rc_timestamp)