Misc: GLX: Avoid using multi-sampling visuals

Avoid using multi-sampled visuals, like the cogl patch:
http://people.freedesktop.org/~glisse/0001-glx-do-not-use-multisample-visual-config-for-front-o.patch

opengl.c

@@ -386,6 +386,14 @@ glx_update_fbconfig(session_t *ps) {
     int id = (int) (pcur - pfbcfgs);
     int depth = 0, depth_alpha = 0, val = 0;
 
+    // Skip over multi-sampled visuals
+    // http://people.freedesktop.org/~glisse/0001-glx-do-not-use-multisample-visual-config-for-front-o.patch
+#ifdef GLX_SAMPLES
+    if (Success == glXGetFBConfigAttrib(ps->dpy, *pcur, GLX_SAMPLES, &val)
+        && val > 1)
+      continue;
+#endif
+
     if (Success != glXGetFBConfigAttrib(ps->dpy, *pcur, GLX_BUFFER_SIZE, &depth)
         || Success != glXGetFBConfigAttrib(ps->dpy, *pcur, GLX_ALPHA_SIZE, &depth_alpha)) {
       printf_errf("(): Failed to retrieve buffer size and alpha size of FBConfig %d.", id);
@@ -446,6 +454,12 @@ glx_update_fbconfig(session_t *ps) {
     printf_errf("(): No FBConfig found for depth 32. Expect crazy things.");
   }
 
+#ifdef DEBUG_GLX
+  printf_dbgf("(): %d-bit: %#3x, 32-bit: %#3x\n",
+      ps->depth, (int) ps->glx_fbconfigs[ps->depth]->cfg,
+      (int) ps->glx_fbconfigs[32]->cfg);
+#endif
+
   return true;
 }