pipeline statistics test: Fix compute shader setup in !GL4.3 case.

pipeline statistics test: Fix compute shader setup in !GL4.3 case.

The ARB_compute_shader spec states a requirement for GL4.2/GLSL 4.20
or better, but we were using "#version 430" regardless, causing a
compile failure on older versions.  Add a variant of the shader using
the ARB_compute_shader extension instead.

I picked GLSL 330 for the variant because the test is included in the
GL 3.3 test set, and Mesa's softpipe driver exposes ARB_compute_shader
on GL 3.3 -- the GLSL requirement in the spec seems to be more than is
actually necessary for compute shaders, assuming you have
ARB_shader_image_load_store and such as well.  Since we're doing this
pre-4.2, we have to add the dependency on ARB_shader_atomic_counters
as well.

VK-GL-CTS Issue: 2694
Components: OpenGL
Affects: KHR-GL33.pipeline_statistics_query_tests_ARB.functional_compute_shader_invocations

Change-Id: If37e0e10bed86281d07aed67394075844e88003d