vcl: Implement basic SalGraphics methods for OpenGL backend

Change-Id: Iade3960c38f0de5594bc98e535450abcf88e9a6d
extract shaders from source code

Conflicts:
	vcl/opengl/gdiimpl.cxx

Change-Id: Ifbb55e58e0854cc491703b8ca8d8e582741a9bd9
vcl: Some fixes to the OpenGL impl

Change-Id: I58466142e0a47beb892e10113c1bc34d5ac3abcd
vcl: Add methods to get size of OpenGLSalGraphicsImpl

Change-Id: I7eecbc236db12fb9453384985245eb5ca781e0f5
vcl: Update OpenGL context before drawing

Change-Id: I7575881d8d9a2026a74692ca562a340231d946bd
vcl: Add OpenGLSalBitmap implementation

Change-Id: I0deebaedf6fe5b23f50a448eea0d5d9e99ebd391
vcl: Remove the extra colon at the end of shader

Change-Id: I0a1a2346176a9f2f4d62ca80a9485d720b522cef
vcl: Get the OpenGL window size from the frame

Change-Id: Id1b62d1982e56ef073ebb4ab800356d4dee3d742
vcl: Fix the vertices calculations for some drawing operations

Change-Id: Ida92d77d7f828f5ff53e7cceaf4787beeef0022b
fix signed/unsigned comparison warning

Change-Id: I0d1ce56514ff9dfff620f11cf987d6d53c4be5e4