* All core types masks are now correctly marked as bitfields.
* The enum hacks in MouseButtonMask and many other types are gone. This ensures that binders to other languages non C++ can actually implement type safe bitmasks.
* Most bitmask operations replaced by functions in BitField<>
* Key is still a problem because its enum and mask at the same time. While it kind of works in C++, this most likely can't be implemented safely in other languages and will have to be changed at some point. Mostly left as-is.
* Documentation and API dump updated to reflect bitfields in core types.