[Libclc-dev] Implement more math builtins

[Tom Stellard]

Hi,

This series implements several more math builtins.  cos/sin
patches require an implementation of fract to work correctly
for doubles.

I have patches to both implement fract and fix fmin, which fract
depends on, but I still get failures in the fract and fmin tests
due to what I think are bugs in the R600/SI compiler.

Even with those bugs, the sin/cos tests still pass with these
broken implementations.

atan2 and atanpi also depend on an ldexp implementation.  For testing,
I just implemented ldexp using the __builtin_amdgpu_ldexp builtin
and these both passed the tests I have.

-Tom