mesa: Fix VAO deletion on GL 3.1 core.
mesa: Fix VAO deletion on GL 3.1 core.

We were calling through a dispatch table entry that was NULL, since the apple
variant is only on legacy desktop.  Just call the function we mean instead of
indirecting through the dispatch.

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