SERVER-15951 CollectionLock should check entire lock heirarchy, not just DB lock
SERVER-14425: fix WriteConflictException handling in multi-update
SERVER-14860: fix multi-index build transactionality around setIndexIsMultikey
SERVER-15892: catch WriteConflictException in findAndModify
SERVER-15948 Fix tests inserting duplicate ts's into oplog
SERVER-15948 Fast OplogStart impl for RSs supporting arbitrary DiskLocs

Storage engines must opt-in to this functionality. For now, heap1 is the only
one to do so.
Merge remote-tracking branch 'upstream/master'