Still trying to get mesa driver test right.

panda/src/glstuff/glGraphicsStateGuardian_src.cxx

@@ -573,7 +573,7 @@ reset() {
 
   _supports_vertex_arrays = true;
   if (_gl_version.find("1.2 (1.5 Mesa 6.",0) != string::npos) {
-    if (_gl_renderer.find(" Mesa ") != string::npos) {
+    if (_gl_renderer.find("Mesa ") == 0) {
       // We suspect this particular version of Mesa, which appears to
       // be installed by default on every Linux implementation, has
       // real problems rendering with vertex arrays.  Therefore,