Use a joinable thread again

This was the original behaviour; I somehow got this wrong in
7e028ed.

Author: bk138

src/wxServDisc.cpp

@@ -515,11 +515,7 @@ wxServDisc::wxServDisc(void* p, const wxString& what, int type)
     return;
   }
 
-#if wxVERSION_NUMBER >= 2905 // 2.9.4 still has a bug here: http://trac.wxwidgets.org/ticket/14626  
-  if( CreateThread(wxTHREAD_DETACHED) != wxTHREAD_NO_ERROR )
-#else
-  if( Create() != wxTHREAD_NO_ERROR )
-#endif
+  if( CreateThread() != wxTHREAD_NO_ERROR )
     err.Printf(_("Could not create scan thread!"));
   else
     if( GetThread()->Run() != wxTHREAD_NO_ERROR )