Add Flx2DInput as a base class for FlxTouch and FlxMouse
Flx2DInput -> FlxPointer
FlxMouse HTML5 fix
FlxPointer: fix for overlaps()
Merge pull request #1099 from Gama11/Flx2DInput

Add FlxPointer as a base class for FlxTouch and FlxMouse, closes #1088