[Piglit] start of GLSL 1.40 testing

[Eric Anholt]

Here are a few tests I've written over the last few days.  Things I
definitely haven't tested:

- New inverse() builtin.

- Other builtins are still present and work.

  This is particularly a concern for texturing.

- VS without gl_Position write

  I've got a WIP test for this using transform feedback.

- UBO support

- TBO support.

  Should one be able to do 1.40 (specifies addition of TBO
  texelFetch()) without TBOs?  Should TBOs be doable without 1.40 or
  EXT_gpu_shader4 by exposing the gpu_shader4 texelFetch?)

- Disallowed mixing 1.40 and fixed function.

- Removal of ftransform().

- changes to mix/isnan/isinf with scalar bools.

  I couldn't really parse what changed here, but it's mentioned in the
  changelog.

- Redeclaration testing.

  Is there any redeclaration to handle?

- ARB_compatibility.

  I'm not interested in ARB_compatibility, nor do I expect Mesa to
  support it, so I haven't done any testing of interactions with it.

2/5] glsl-1.40: Add tests for minimum maximum constants.  GIT: [PATCH
3/5] glsl-1.40: Add tests for removal of deprecated builtin GIT:
[PATCH 4/5] glsl-1.40: Add some tests for ARB_texture_rectangle GIT:
[PATCH 5/5] glsl-1.40: New test for discard exiting the shader.