glx: Drop broken drawable garbage collection

Doesn't work for pixmaps, was looking up the GLX XID and was never thread
safe.  Instead, just destroy the client side structures when the
drawable is no long current for a context.

src/glx/dri2.c

@@ -175,6 +175,14 @@ DRI2Error(Display *display, xError *err, XExtCodes *codes, int *ret_code)
 	err->minorCode == X_DRI2CopyRegion)
 	return True;
 
+    /* If the X drawable was destroyed before the GLX drawable, the
+     * DRI2 drawble will be gone by the time we call
+     * DRI2DestroyDrawable.  So just ignore BadDrawable here. */
+    if (err->majorCode == codes->major_opcode &&
+	err->errorCode == BadDrawable &&
+	err->minorCode == X_DRI2DestroyDrawable)
+	return True;
+
     return False;
 }