Fix an "overflow in implicit constant conversion" warning in mEndPrimitive when more warning flags are enabled (such as in the DRI tree).  Make the second line prettier, too.
Fix an "overflow in implicit constant conversion" warning in mEndPrimitive when
more warning flags are enabled (such as in the DRI tree).  Make the second line
prettier, too.

Reported by:	ajax

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