Don't use MESA_EGL_NO_X11_HEADERS

Summary:
With recent Mesa updates (19.2.1), MESA_EGL_NO_X11_HEADERS doesn't have
any effect. So, let's include fixx11h.h instead.

Test Plan: I am able to build kwin once again.

Reviewers: #kwin, davidedmundson

Reviewed By: #kwin, davidedmundson

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D24840

plugins/qpa/eglhelpers.h

@@ -20,9 +20,9 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 #pragma once
 
-#define MESA_EGL_NO_X11_HEADERS
 #include <epoxy/egl.h>
 #include "fixqopengl.h"
+#include <fixx11h.h>
 
 #include <QSurfaceFormat>
 

plugins/qpa/offscreensurface.h

@@ -20,9 +20,9 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 #pragma once
 
-#define MESA_EGL_NO_X11_HEADERS
 #include <epoxy/egl.h>
 #include "fixqopengl.h"
+#include <fixx11h.h>
 
 #include <qpa/qplatformoffscreensurface.h>