[Piglit] [PATCH] tests/glslparsertest/glsl2: Unsigned array index test

[tiffany]

Sorry, I've moved it to a proper location. The README and HACKING documents
didn't give much indication of how and where to make tests, so I picked the
first spot I saw that contained glsl shaders.

This test is only a little bit different from the one which was already present
at tests/spec/glsl/1.30/compiler/structure-and-array-operations/array-index-as-uint.vert,
but it appears as though the first one does not trigger the assertion which
I created this test for. It must go through a path other than the one in
lower_variable_index_to_cond_assign.cpp.