Bug 770535, part 1 - Remove map lock from XPConnect. r=bholley
Bug 770535, part 2 - Replace ThreadRunningGC with GCIsRunning. r=bholley
Bug 770535, part 3 - Fold mMainThreadWrappedNativeProtoMap into mWrappedNativeProtoMap. r=bholley

    With the removal of locks, these two maps are identical.