Move window_event_result definition to event.h

The whole event system will need to know about window_event_result, because every event function will return one.

common/include/event.h

@@ -48,6 +48,17 @@ enum event_type : unsigned
 	EVENT_UI_USERBOX_DRAGGED
 };
 
+enum class window_event_result : unsigned
+{
+	// Window ignored event.  Bubble up.
+	ignored,
+	// Window handled event.
+	handled,
+	close,
+	// Window handler already deleted window (most likely because it was subclassed), don't attempt to re-delete
+	deleted,
+};
+
 // A vanilla event. Cast to the correct type of event according to 'type'.
 struct d_event
 {

common/include/fwd-window.h

@@ -19,7 +19,6 @@ void arch_init();
 namespace dcx {
 
 class window;
-enum class window_event_result : unsigned;
 
 template <typename T>
 using window_subfunction = window_event_result (*)(window *menu,const d_event &event, T *userdata);

common/include/window.h

@@ -21,19 +21,9 @@
 
 #ifdef __cplusplus
 #include "fwd-window.h"
+#include "event.h"
 namespace dcx {
 
-enum class window_event_result : unsigned
-{
-	// Window ignored event.  Bubble up.
-	ignored,
-	// Window handled event.
-	handled,
-	close,
-	// Window handler already deleted window (most likely because it was subclassed), don't attempt to re-delete
-	deleted,
-};
-
 constexpr const unused_window_userdata_t *unused_window_userdata = nullptr;
 
 struct embed_window_pointer_t