This allows a driver to support all three variations of two-sided stencil
including GL_ATI_separate_stencil, GL_EXT_stencil_two_side and OpenGL 2.0
<li>GL_EXT_vertex_array_bgra extension (software drivers, i965 driver)
-<li>GL_NV_texture_env_combine4 extension (software drivers, i965 driver)
+<li>GL_NV_texture_env_combine4 extension (software drivers, i965/i915 drivers)
+<li>GL_EXT_texture_swizzle extension (software drivers, i965 driver)
</ul>