Fix: Flush module prefs after a change.

This ensures that the config file remembers a 'fail to load'.  We set status to fail before loading a module, that now gets written out to the config file because we flush prefs, the dodgy module loads and crashes, and next time Audacity knows it's a fail.  If instead the module loads and does not crash on load, the original status (enabled or ask) is written back to the config file.

src/prefs/ModulePrefs.cpp

@@ -151,6 +151,7 @@ void ModulePrefs::SetModuleStatus( wxString fname, int iStatus ){
    wxString ShortName = wxFileName( fname ).GetName();
    wxString PrefName = wxString( wxT("/Module/") ) + ShortName.Lower();
    gPrefs->Write( PrefName, iStatus );
+   gPrefs->Flush();
 }