vcl: Fix pixel drawing with OpenGL

Change-Id: I5d8e80baec9537e0c5913d821e26566409fe5261
vcl: Add methods to call before and after OpenGL rendering

Change-Id: I937907a3e8eb8f841a2eed6199e86d022be7dc16
vcl: Remove unused shaders list

Change-Id: I13a25a39cceb184c2bb2b48bc143a951ee982b26
vcl: Use a different FBO when rendering using a VirtualDevice

Change-Id: I8cb97a4057c06ca09adfcac8dcd3f61ac9508430
vcl: Fix alpha value when drawing bitmap with mask

Change-Id: Ie9cbd754383296a9fe6e42346d4a17477eb88242
vcl: Fix the VirtualDevice rectangle rendering in vcldemo

Change-Id: I43d43d5e81d52560154b102cc469761b51a590d4
vcl: Fix text rendering with OpenGL

Change-Id: I7784fa81cb6f9a3d6437b2b628c37e7895c84733