Improve ID documentation and add more links to it

Better describe various kinds of IDs and advise not to use hard-coded
values of them.

interface/wx/window.h

@@ -358,6 +358,7 @@ public:
             Pointer to a parent window.
         @param id
             Window identifier. If wxID_ANY, will automatically create an identifier.
+            See @ref overview_windowids for more information about IDs.
         @param pos
             Window position. wxDefaultPosition indicates that wxWidgets
             should generate a default position for the window.