vcl: Implement drawing of transformed bitmaps in OpenGL backend

Change-Id: I79717a608f33050b84244e378a6e51bd3be29232
vcl: Fix DrawMask implementation in OpenGL backend

Change-Id: Idc0bedaba5a4cea351f131d402c2b1093ac1c53c
windows opengl: Use the updated DrawMask to get nice text with OpenGL.

Change-Id: Ie4f08575848e76159af86d44e10f24fa383930fb