st/mesa: improve the guess_and_alloc_texture() heuristic
st/mesa: improve the guess_and_alloc_texture() heuristic

If GL_BASE_LEVEL==0 and GL_MAX_LEVEL==0 that's a pretty good hint that
there'll be a single mipmap level in the texture.

Google Earth sets the texture's state this way before the first glTexImage
call.  This saves a bit of texture memory.

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