use DeferWindowPos() instead of MoveWindow() if possible; always use WS_CLIPCHILDREN; never use WS_CLIPSIBLINGS

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@31076 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/window.h

@@ -422,6 +422,10 @@ protected:
     // the old window proc (we subclass all windows)
     WXFARPROC             m_oldWndProc;
 
+    // the current multi-window move structure handle, NULL if window resize is
+    // not in process
+    WXHANDLE              m_hDWP;
+
     // additional (MSW specific) flags
     bool                  m_mouseInWindow:1;
     bool                  m_lastKeydownProcessed:1;