Add new methods to transform coordinates expressed in Cocoa's bounds rect to

Add new methods to transform coordinates expressed in Cocoa's bounds rect to
and from those expressed in wxWidgets fashion.  Use these new methods to do
the translation for mouse events, child window position, and dirty rects.
Also improve DoMoveWindow to only dirty the old and new rects of the
control within its superview rather than the entire superview.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@31332 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775