translate_test: improve
translate_test: improve

1. Generate random data specifically for float and doubles, so that
   they end up in [0, 1] range
2. Don't test useless conversions like SCALED <-> NORM
3. Poison the buffers before testing

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