WIP: loop analysis tests
glapi: Rename ARB_compute_shader "LOCAL" -> "WORK_GROUP".

The piglit glapi files, which are derived from files published on
www.opengl.org, contained nonstandard names for two enums:
COMPUTE_LOCAL_WORK_SIZE and MAX_COMPUTE_LOCAL_INVOCATIONS.

The ARB_compute_shader spec, the OpenGL specs, and the OpenGL wiki all
agree that these should be called COMPUTE_WORK_GROUP_SIZE and
MAX_COMPUTE_WORK_GROUP_INVOCATIONS.  So rename them in piglit to be
consistent.
util: Add ARB_compute_shader support to piglit_get_gl_enum_name().
Add minmax test for ARB_compute_shader.
Test compilation rules related to compute shader layout qualifiers.
Test that compute shader work group sizes are properly bounds checked.
Test ARB_compute_shader built-in constant gl_WorkGroupSize.
Test ARB_compute_shader built-in constant gl_MaxComputeWorkGroupCount.
Test ARB_compute_shader built-in constant gl_MaxComputeWorkGroupSize.
Test that compute shaders may not have user-defined ins/outs.
shader_runner: Add support for compute shaders.

Currently there is no way for shader_runner to accept output from
compute shaders; however this should still be useful for linker tests.
Linker tests for compute shaders: local work sizes.

These tests verify the linker rules for local work sizes (they must be
specified in at least one shader, and they must not conflict).
Test API errors for compute shaders related to COMPUTE_WORK_GROUP_SIZE query.

This test can be expanded in the future to check for other compute
shader API errors.