- Rename WIN_Handle16 to HWDN_16 and make it a macro.
- Prepare user.dll for the change of HWND to a void*.

diff --git a/windows/mdi.c b/windows/mdi.c
index bc0f87b..05d2f2d 100644
--- a/windows/mdi.c
+++ b/windows/mdi.c
@@ -566,7 +566,7 @@
         seg_cs16 = MapLS( &cs16 );
         hwnd = WIN_Handle32( CreateWindow16( cs->szClass, cs->szTitle, style,
                                              cs16.x, cs16.y, cs16.cx, cs16.cy,
-                                             WIN_Handle16(parent), (HMENU)wIDmenu,
+                                             HWND_16(parent), (HMENU)wIDmenu,
                                              cs16.hOwner, (LPVOID)seg_cs16 ));
         UnMapLS( seg_cs16 );
         UnMapLS( title );
@@ -1447,7 +1447,7 @@
             MDINEXTMENU next_menu;
             DefFrameProcW( WIN_Handle32(hwnd), WIN_Handle32(hwndMDIClient),
                            message, wParam, (LPARAM)&next_menu );
-            return MAKELONG( next_menu.hmenuNext, WIN_Handle16(next_menu.hwndNext) );
+            return MAKELONG( next_menu.hmenuNext, HWND_16(next_menu.hwndNext) );
         }
     default:
         return DefWindowProc16(hwnd, message, wParam, lParam);
@@ -1614,7 +1614,7 @@
         {
             MDINEXTMENU next_menu;
             DefMDIChildProcW( WIN_Handle32(hwnd), message, wParam, (LPARAM)&next_menu );
-            return MAKELONG( next_menu.hmenuNext, WIN_Handle16(next_menu.hwndNext) );
+            return MAKELONG( next_menu.hmenuNext, HWND_16(next_menu.hwndNext) );
         }
     default:
         return DefWindowProc16(hwnd, message, wParam, lParam);