Revert "i965: Do FS SLT, SGT, and friends using CMP, SEL instead of CMP, MOV, MOV."
Revert "i965: Do FS SLT, SGT, and friends using CMP, SEL instead of CMP, MOV, MOV."

This reverts commit 46450c1f3f93bf4dc96696fc7e0f0eb808d9c08a.  I was
wrong about null reg behavior -- it reads undefined, not 0.  And
they're not kidding.

wolf96/glsl-optimizer,mapbox/glsl-optimizer,djreep81/glsl-optimizer,mcanthony/glsl-optimizer,benaadams/glsl-optimizer,adobe/glsl2agal,mcanthony/glsl-optimizer,jbarczak/glsl-optimizer,benaadams/glsl-optimizer,KTXSoftware/glsl2agal,KTXSoftware/glsl2agal,zeux/glsl-optimizer,zz85/glsl-optimizer,benaadams/glsl-optimizer,mcanthony/glsl-optimizer,mapbox/glsl-optimizer,dellis1972/glsl-optimizer,zz85/glsl-optimizer,metora/MesaGLSLCompiler,zeux/glsl-optimizer,KTXSoftware/glsl2agal,zz85/glsl-optimizer,zz85/glsl-optimizer,jbarczak/glsl-optimizer,mcanthony/glsl-optimizer,jbarczak/glsl-optimizer,benaadams/glsl-optimizer,djreep81/glsl-optimizer,tokyovigilante/glsl-optimizer,djreep81/glsl-optimizer,metora/MesaGLSLCompiler,adobe/glsl2agal,jbarczak/glsl-optimizer,dellis1972/glsl-optimizer,bkaradzic/glsl-optimizer,adobe/glsl2agal,benaadams/glsl-optimizer,adobe/glsl2agal,djreep81/glsl-optimizer,tokyovigilante/glsl-optimizer,bkaradzic/glsl-optimizer,zeux/glsl-optimizer,wolf96/glsl-optimizer,zeux/glsl-optimizer,tokyovigilante/glsl-optimizer,benaadams/glsl-optimizer,metora/MesaGLSLCompiler,zz85/glsl-optimizer,zz85/glsl-optimizer,tokyovigilante/glsl-optimizer,bkaradzic/glsl-optimizer,wolf96/glsl-optimizer,bkaradzic/glsl-optimizer,mapbox/glsl-optimizer,KTXSoftware/glsl2agal,mapbox/glsl-optimizer,wolf96/glsl-optimizer,djreep81/glsl-optimizer,zeux/glsl-optimizer,dellis1972/glsl-optimizer,dellis1972/glsl-optimizer,KTXSoftware/glsl2agal,mapbox/glsl-optimizer,tokyovigilante/glsl-optimizer,bkaradzic/glsl-optimizer,adobe/glsl2agal,dellis1972/glsl-optimizer,mcanthony/glsl-optimizer,wolf96/glsl-optimizer,jbarczak/glsl-optimizer