Fixed legally the oldest bugemon in DisplayObject.

Strangely (or not so strangely), the bug has never shown itself. Perhaps
because almost everything is enclosed in zero-size containers. Will
investigate this matter later.
Matrix now has pooling functions.

Mostly for internal use. Will migrate most of code to use this later.
Even more MouseEvent corrections.

I'm starting to slightly dislike MouseEvent.MOUSE_MOVE.
Fixed some things about style.setProperty use.