Added wxMessageOutput as per the discussion on wx-dev.

Added wxApp::DoInit to initialize the global wxMessageOutput instance.
Changed wxCommandLineParser to use wxMessageOutput.


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@16267 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/cmdline.h

@@ -202,6 +202,9 @@ public:
     static wxArrayString ConvertStringToArgs(const wxChar *cmdline);
 
 private:
+    // get usage string
+    wxString GetUsageString();
+
     // common part of all ctors
     void Init();