[Piglit] Python errors during test generation

[Chad Versace]

Paul,

I observed these Python errors during test generation. I haven't had a chance to look into them yet, but just wanted to inform you before I forgot about them.

[87/1749] Generating builtin_uniform_tests.list
/home/chad/proj/linux/graphics/v/master/src/piglit/generated_tests/builtin_function.py:1146: RuntimeWarning: overflow encountered in uint_scalars
  f('op-sub', 2, 110, lambda x, y: x - y, match_simple_binop, [floats+vecs+mats+ints+ivecs+uints+uvecs, floats+vecs+mats+ints+ivecs+uints+uvecs], template = '({0} - {1})')
[127/1749] Generating constant_array_size_tests.list
/home/chad/proj/linux/graphics/v/master/src/piglit/generated_tests/builtin_function.py:1146: RuntimeWarning: overflow encountered in uint_scalars
  f('op-sub', 2, 110, lambda x, y: x - y, match_simple_binop, [floats+vecs+mats+ints+ivecs+uints+uvecs, floats+vecs+mats+ints+ivecs+uints+uvecs], template = '({0} - {1})')