glsl: Allow implicit int -> uint conversions for the % operator.

glsl: Allow implicit int -> uint conversions for the % operator.

GLSL 4.00 and GL_ARB_gpu_shader5 introduced a new int -> uint implicit
conversion rule and updated the rules for modulus to use them.  (In
earlier languages, none of the implicit conversion rules did anything
relevant, so there was no point in applying them.)

This allows expressions such as:

   int foo;
   uint bar;
   uint mod = foo % bar;

Cc: mesa-stable@lists.freedesktop.org
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>