intel: Fix crash in automatic mipmap generation for glCopyTex{Sub,}Image.
intel: Fix crash in automatic mipmap generation for glCopyTex{Sub,}Image.

The images aren't mapped at this point, so we want the generic Mesa path for
GenerateMipmapEXT that does the mapping/unmapping for us.  Ideally Mesa would
just call it for us.

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