Some tests fail under mesa, need to ask for GL core context for GLSL 1.50 support

[stuaxo]

Using pull request #63 I was able to build in Linux, some of the tests fail under mesa -

test array-globalconst-init-in.txt
  glsl compile error:
0:1(10): error: GLSL 1.50 is not supported. Supported versions are: 1.10, 1.20, 1.30, 1.00 ES, and 3.00 ES

Mesa does support GLSL 1.50, but you need to ask for a core context, if you use the workaround of overridding the GL version, they all pass -

MESA_GL_VERSION_OVERRIDE=3.3 MESA_GLSL_VERSION_OVERRIDE=330 ./hlsl2glsltest ../tests/

The solution is that the tests need to ask for the right version by setting the correct window hints.

[computerquip]

This is a one or two line fix which requires a FreeGLUT extension. I'll submit a pull request sometime today.

[computerquip]

The solution was a little more ugly than I thought it would be. I clearly forgot how disgusting GL version testing can be... Anyways, I won't be making a pull request until #63 is in place since the fix for this required that commit in order to test and build.

Until then though, please test on the branch mesa-tests in my tree or https://github.com/computerquip/hlsl2glslfork/tree/mesa-tests

[computerquip]

Pull request here: #66