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

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@38945 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msdos/utilsdos.cpp

@@ -21,12 +21,12 @@
     #include "wx/string.h"
     #include "wx/intl.h"
     #include "wx/log.h"
+    #include "wx/app.h"
 #endif
 
 #include "wx/apptrait.h"
 #include "wx/process.h"
 #include "wx/confbase.h"        // for wxExpandEnvVars()
-#include "wx/app.h"
 #include "wx/cmdline.h"
 #include "wx/filename.h"
 #include "wx/wfstream.h"