mesa: Make bitset.h not rely on Mesa-specific types and functions.
mesa: Make bitset.h not rely on Mesa-specific types and functions.

Note that we can't use u_math.h's align() because it's a function instead
of a macro, while BITSET_DECLARE needs a constant expression for nouveau's
usage in global declarations.

v2: Stick some parens around the bits macro argument usage (review by Jose).

Reviewed-by: Jose Fonseca <61b5a29db2c0650f7c8510f93eece059c1b09320@vmware.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler