mesa: create compat symlinks for glew

x11/mesa/mesa.conf

@@ -23,3 +23,12 @@ if ! pkginstalled freeglut; then
 		cd -
 	}
 fi
+
+mesa_symlinks() {
+	cd $root/usr/lib
+	ln -sdfv ../X11/include/GL $root/usr/include/GL
+	ln -sfv ../X11/${libdir##*/}/libGL.* .
+	ln -sfv ../X11/${libdir##*/}/libGLU.* .
+}
+
+hook_add postmake 5 mesa_symlinks