meta: Use a #define for the vector type to avoid %svec4 everywhere.

meta: Use a #define for the vector type to avoid %svec4 everywhere.

By adding "#define gvec4 %svec4" to the top of our fragment shader, we
can write generic code without needing to specialize it to vec4, ivec4,
or uvec4 via asprintf.

This also makes the INT and UNSIGNED_INT merge function code identical,
so I combined those two cases.

It's not a big savings, but a little bit tidier.

v2: Rebase on Vinson's MSVC build fixes.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>