util: import public domain code for integer division by a constant

util: import public domain code for integer division by a constant

Compilers can use this to generate optimal code for integer division
by a constant.

Additionally, an unsigned division by a uniform that is constant but not
known at compile time can still be optimized by passing 2-4 division
factors to the shader as uniforms and executing one of the fast_udiv*
variants. The signed division algorithm doesn't have this capability.

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>