* Re-applying r34449, r34500 and r34518 which Brion reverted by accident

* Re-applying r34449, r34500 and r34518 which Brion reverted by accident
* Adding ApiQueryBase::addJoinConds() as wrapper for Database::select()'s $join_conds parameter
* Migrating query modules to addJoinConds()
* Using implicit join rather than INNER JOIN in ApiQueryBacklinks
* Using FORCE INDEX (times) on logging table in ApiQueryLogEvents; although MySQL 4 seems to pick this index automatically (evidenced by the fact the WMF servers are still alive), MySQL 5 doesn't and filesorts
* Replacing LEFT JOIN with implicit (inner) join in ApiQueryContributions: revisions without a corresponding page table entry shouldn't be shown anyway