Remove unnecessary c_str() from wx var arg functions arguments

Using c_str() for arguments to wxString::Printf(), Format() and
wxLogXXX() is useless since wx 2.9 days, so simply remove them.

No real changes, this is just a (long due) cleanup.

src/msw/textctrl.cpp

@@ -742,7 +742,7 @@ void wxTextCtrl::AdoptAttributesFromHWND()
         wxChar c;
         if ( wxSscanf(classname, wxT("RichEdit%d0%c"), &m_verRichEdit, &c) != 2 )
         {
-            wxLogDebug(wxT("Unknown edit control '%s'."), classname.c_str());
+            wxLogDebug(wxT("Unknown edit control '%s'."), classname);
 
             m_verRichEdit = 0;
         }