wayland: split headers and distribute structure definitions

Instead of having all structures in one huge headers, move them
in the appropriate place, and create one header for surface state.

https://bugzilla.gnome.org/show_bug.cgi?id=707128

src/wayland/meta-wayland-pointer.c

@@ -44,6 +44,7 @@
 #include "config.h"
 
 #include "meta-wayland-pointer.h"
+#include "meta-wayland-private.h"
 
 #include <string.h>