Bug 1550422 - P0. Use X11UndefineNone.h to avoid conflicts with the macro None from X11/X.h. r=karlt

Differential Revision: https://phabricator.services.mozilla.com/D31971

--HG--
extra : moz-landing-system : lando

toolkit/xre/nsX11ErrorHandler.h

@@ -5,6 +5,7 @@
 
 #ifdef MOZ_X11
 #  include <X11/Xlib.h>
+#  include "X11UndefineNone.h"  // Unset some macros defined by X.h included by Xlib.h
 
 /**
  * InstallX11ErrorHandler is not suitable for processes running with GTK3 as