llvmpipe: Work without sse2 if llvm is new enough
llvmpipe: Work without sse2 if llvm is new enough

At least on llvm 3.2 this appears to work fine.  Tested on an Athlon XP
2600+, which has sse and 3dnow but not sse2.

Reviewed-by: Jose Fonseca <61b5a29db2c0650f7c8510f93eece059c1b09320@vmware.com>
Signed-off-by: Adam Jackson <4482611cc290c2ce1399431891dcb9221c95f994@redhat.com>

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