Fix build with wxGTK 3.0

--- src/common/myintl.cpp

+++ src/common/myintl.cpp

@@ -1060,7 +1060,7 @@ static wxString GetFullSearchPath(const wxChar *lang)

     wxString wxp = wxGetInstallPrefix();

     if ( !wxp.empty() )

     {

-        wxp = GetMsgCatalogSubdirs(wxp + _T("/share/locale"), lang);

+        wxp = GetMsgCatalogSubdirs((wxp + _T("/share/locale")).wchar_str(), lang);

         if ( paths.Index(wxp) == wxNOT_FOUND )

             paths.Add(wxp);

     }