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/common/docview.cpp

@@ -40,6 +40,7 @@
     #include "wx/intl.h"
     #include "wx/log.h"
     #include "wx/msgdlg.h"
+    #include "wx/mdi.h"
 #endif
 
 #include "wx/ffile.h"
@@ -48,10 +49,6 @@
     #include "wx/filename.h"
 #endif
 
-#ifdef __WXGTK__
-    #include "wx/mdi.h"
-#endif
-
 #if wxUSE_PRINTING_ARCHITECTURE
     #include "wx/prntbase.h"
     #include "wx/printdlg.h"