Blender Git Loki

Refactor to recent matcap built-ins to not use the built in system.
Those variables would get declared on fragment shader level and since we
use reserved opengl variables, some compilers would throw an error
(NVIDIA allows, some ATI compilers may break). Instead, use a separate
opengl built-in category especially for them. This works on NVIDIA, and
will wait for tests of this commit from ATI users.