driconf: add a miscellaneous section and always_have_depth_buffer option
driconf: add a miscellaneous section and always_have_depth_buffer option

This option is needed for some applications that neglect to request
a depth buffer when choosing a visual/fbconfig.

The Linux app Topogun is an example of this problem.

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