i965/vec4/nir: implement double comparisons
i965/vec4/nir: implement double comparisons

v2:
- Added newline before if() (Matt)

Reviewed-by: Matt Turner <789b315743a28dd066a4ba1459c35951c291d8a6@gmail.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler