further reduction of include dependencies, also finalised some classes

rtgui/editbuffer.h

@@ -19,9 +19,14 @@
 #pragma once
 
 #include "editid.h"
-#include "../rtengine/coord.h"
 #include <cairomm/cairomm.h>
 
+namespace rtengine {
+
+struct Coord;
+
+}
+
 class EditDataProvider;
 class EditSubscriber;