Tested by Crucible "func.depthstencil.stencil_triangles.*" in
commit c194292d5eadb84e9d7489fc01ce0b653cdd4ca5 (HEAD -> master)
Author: Chad Versace <chad.versace@intel.com>
Date: Wed Nov 4 16:19:24 2015 -0800
Subject: func.depthstencil: Remove stencil clear workaround for Mesa