Remove needless uses of wxString::c_str() in wxString::Format...

... and similar wx "variadics," which all treat wxString smartly enough that
you don't need this.

Don't need c_str either to convert wxString to const wxChar * because
wxString has a conversion operator that does the same.

src/widgets/HelpSystem.cpp

@@ -361,9 +361,9 @@ void HelpSystem::ShowHelp(wxWindow *parent,
 #endif
 
    wxLogMessage(wxT("Help button pressed: PageName %s, releasePageName %s"),
-              PageName.c_str(), releasePageName.c_str());
+              PageName, releasePageName);
    wxLogMessage(wxT("webHelpPage %s, localHelpPage %s"),
-              webHelpPage.c_str(), localHelpPage.c_str());
+              webHelpPage, localHelpPage);
 
    wxASSERT(parent); // to justify safenew