CELL: fix use of stencil value mask
CELL: fix use of stencil value mask

The Cell stencil tests were completely ignoring the stencil value mask.
Now the original code paths are still used if the stencil value mask
is all 1s; but code to use the mask for the stencil value and reference
value comparisons is now emitted if the mask is not all 1s.

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