EXT_gpu_shader4 lets us say “noperspective” in GLSL #version 120 just
like in later GLSL.
Mac shader now matches modern GLSL available on other platforms.
The first two of several new simple built-in shaders (will test these
before adding more). These are intended for the new immediate mode API,
but you can use them just like any built-in GPUShader.
Due to limitations on different platforms, shaders need to work with
GLSL versions 120, 130 and 150. Final Blender 2.8 will be pure #version
150.
