Bug 909514 - Include <new> before mozilla::Maybe (and move Maybe into mfbt/Maybe.h).
Fixing VectorQueue bugs, adding tests.
Fixing bugs in MaybeWeak*.
Making nsObserverList behave like it used to.
Add removeAt() function to VectorQueue.
Add RemovePreferringStronRefs() to MaybeWeakMultiset.
Use RemovePreferringWeakRefs to nsObserverList.
Move MaybeWeakSet's finalizer out of the code.
Add (failing) gtest for MaybeWeakSet.