dri: attempt to actually refcount the __DRIDrawable
dri: attempt to actually refcount the __DRIDrawable

valgrind was showing a race between the drawable getting destroyed
by the X resource freeing code, and the context getting destroyed
later and freeing the drawable.

However I've no idea if some other combination of things could cause
this code to leak.

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