Mention that wxDialog::SetEscapeId() can't be used for native dialogs.

Native dialogs handling of Esc can't be customized (definitely not easily,
and possibly not at all).

See #16521.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@77525 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/dialog.h

@@ -495,6 +495,11 @@ public:
         @a id is wxID_NONE meaning that @c ESC presses should be ignored. If
         any other value is given, it is interpreted as the id of the button to
         map the escape key to.
+
+        @note This method should be used for custom modal dialog implemented in
+        wxWidgets itself, native dialogs such as wxMessageDialog or
+        wxFileDialog, handle @c ESC presses in their own way which cannot be
+        customized.
     */
     void SetEscapeId(int id);