docs: Move documentation to inline comments: event_structs

All the GDK documentation is now moved to inline comments

docs/reference/gdk/tmpl/.gitignore

@@ -4,6 +4,7 @@ cursors.sgml
 dnd.sgml
 drawing.sgml
 events.sgml
+event_structs.sgml
 gdkapplaunchcontext.sgml
 gdkdisplay.sgml
 gdkdisplaymanager.sgml

gdk/gdktypes.h

@@ -120,6 +120,12 @@ typedef struct _GdkAtom            *GdkAtom;
  */
 #define GDK_NONE            _GDK_MAKE_ATOM (0)
 
+/**
+ * GdkNativeWindow:
+ *
+ * Used to represent native windows (<type>Window</type>s for the X11
+ * backend, <type>HWND</type>s for Win32).
+ */
 #ifdef GDK_NATIVE_WINDOW_POINTER
 typedef gpointer GdkNativeWindow;
 #else