glsl: #include c99_math.h instead of core.h
glsl: #include c99_math.h instead of core.h

We only need the M_LOG2E definition.

Reviewed-by: Matt Turner <789b315743a28dd066a4ba1459c35951c291d8a6@gmail.com>
Reviewed-by: Jose Fonseca <61b5a29db2c0650f7c8510f93eece059c1b09320@vmware.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler