fix EDA_ITEM::Show() prototype bug, fix KICAD_PLUGIN::Save() problem with netclasses.

eeschema/class_netlist_object.cpp

@@ -94,7 +94,7 @@ const char* ShowType( NETLIST_ITEM_T aType )
 }
 
 
-void NETLIST_OBJECT::Show( std::ostream& out, int ndx )
+void NETLIST_OBJECT::Show( std::ostream& out, int ndx ) const
 {
     wxString path = m_SheetList.PathHumanReadable();
 
@@ -114,8 +114,10 @@ void NETLIST_OBJECT::Show( std::ostream& out, int ndx )
     switch( m_Type )
     {
     case NET_PIN:
+        /* GetRef() needs to be const
         out << " <refOfComp>" << ((SCH_COMPONENT*)m_Link)->GetRef(&m_SheetList).mb_str()
             << "</refOfComp>\n";
+        */
 
         if( m_Comp )
             m_Comp->Show( 1, out );