Include wx/mdi.h according to precompiled headers of wx/wx.h (with other minor cleaning).

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@39644 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/aui/framemanager.cpp

@@ -35,16 +35,13 @@
     #include "wx/dcclient.h"
     #include "wx/dcscreen.h"
     #include "wx/toolbar.h"
+    #include "wx/mdi.h"
 #endif
 
 //#include "wx/dcbuffer.h"
 
 #include "wx/image.h"
 
-#if wxUSE_MDI
-     #include "wx/mdi.h"
-#endif
-
 WX_CHECK_BUILD_OPTIONS("wxAUI")
 
 #include "wx/arrimpl.cpp"