This exhaustively tests all of GLSL 1.30's textureSize variants, both in
the vertex and fragment shaders.  It covers:
- Sampler data type (floating point, signed integer, unsigned integer)
- Dimensionality (1D, 2D, 3D, Cube, 1DArray, 2DArray)
- Color and shadow samplers
- Mipmapped textures
- Non-power-of-two textures

It doesn't cover texture format variations.  In fact, the test never
actually provides any content for the textures, because it should be
irrelevant for textureSize(), is easier to program, and also extra mean.

The new "textureSize" binary takes two arguments: shader stage and
sampler type.  For example:

./bin/textureSize fs sampler1DArrayShadow
./bin/textureSize vs usamplerCube

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Anholt <eric@anholt.net>