Clean up include macros mess

The order and way include macros were structured was chaotic, with no
real common thread between files. Try to tidy up the mess with some
common scheme, to make things look less messy.

src/wayland/meta-wayland-buffer.c

@@ -24,21 +24,20 @@
 
 #include "config.h"
 
-#include "meta-wayland-buffer.h"
-#include "meta-wayland-dma-buf.h"
-
-#include <clutter/clutter.h>
-#include <cogl/cogl-egl.h>
-#include <meta/util.h>
+#include "wayland/meta-wayland-buffer.h"
 
 #include <drm_fourcc.h>
 
+#include "backends/meta-backend-private.h"
+#include "clutter/clutter.h"
+#include "cogl/cogl-egl.h"
+#include "meta/util.h"
+#include "wayland/meta-wayland-dma-buf.h"
+
 #ifndef DRM_FORMAT_MOD_INVALID
 #define DRM_FORMAT_MOD_INVALID ((1ULL << 56) - 1)
 #endif
 
-#include "backends/meta-backend-private.h"
-
 enum
 {
   RESOURCE_DESTROYED,