assign new IDs to plugin copies on paste.

when copying a plugin the state is transferred by serializing
XML and setting state from XML. This state includes the unique ID.

This ID needs to be identical at first in order to load
the state from <session-dir>/plugins/<ID>/*

gtk2_ardour/processor_box.cc

@@ -2155,9 +2155,10 @@ ProcessorBox::paste_processor_state (const XMLNodeList& nlist, boost::shared_ptr
 				/* XXX its a bit limiting to assume that everything else
 				   is a plugin.
 				*/
-
 				p.reset (new PluginInsert (*_session));
-                                p->set_state (**niter, Stateful::current_state_version);
+				PBD::ID id = p->id();
+				p->set_state (**niter, Stateful::current_state_version);
+				boost::dynamic_pointer_cast<PluginInsert>(p)->update_id (id);
 			}
 
 			copies.push_back (p);

libs/ardour/ardour/plugin_insert.h

@@ -53,6 +53,7 @@ class LIBARDOUR_API PluginInsert : public Processor
 	XMLNode& state(bool);
 	XMLNode& get_state(void);
 	int set_state(const XMLNode&, int version);
+	void update_id (PBD::ID);
 
 	void run (BufferSet& in, framepos_t start_frame, framepos_t end_frame, pframes_t nframes, bool);
 	void silence (framecnt_t nframes);

libs/ardour/plugin_insert.cc

@@ -1145,6 +1145,15 @@ PluginInsert::set_state(const XMLNode& node, int version)
 	return 0;
 }
 
+void
+PluginInsert::update_id (PBD::ID id)
+{
+	set_id (id.to_s());
+	for (Plugins::iterator i = _plugins.begin(); i != _plugins.end(); ++i) {
+		(*i)->set_insert_id (id);
+	}
+}
+
 void
 PluginInsert::set_parameter_state_2X (const XMLNode& node, int version)
 {