swrast: add lod bias when texture sampling
swrast: add lod bias when texture sampling

Mostly fixes progs/demos/lodbias when MESA_TEX_PROG=1.  But the LOD still
seems off by -1 or so.
May be an issue with the params passed to _swrast_compute_lambda()

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