mesa: Add driver hooks for texture image mapping/unmapping.
mesa: Add driver hooks for texture image mapping/unmapping.

ctx->Driver.MapTextureImage() / UnmapTextureImage() will be called by
the glTex[Sub]Image(), glGetTexImage() functions, etc. when we're
accessing texture data, and also for software rendering when accessing
texture data.

Reviewed-by: Brian Paul <3cb4e1df5ec4da2c7c4af7c52cec8cf340a55a10@vmware.com>

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