move RecordState enum from ARDOUR::Session to ARDOUR so we can use it in TriggerBox (libs)

libs/surfaces/push2/push2.cc

@@ -736,15 +736,15 @@ Push2::notify_record_state_changed ()
 	}
 
 	switch (session->record_status ()) {
-	case Session::Disabled:
+	case Disabled:
 		b->second->set_color (LED::White);
 		b->second->set_state (LED::NoTransition);
 		break;
-	case Session::Enabled:
+	case Enabled:
 		b->second->set_color (LED::Red);
 		b->second->set_state (LED::Blinking4th);
 		break;
-	case Session::Recording:
+	case Recording:
 		b->second->set_color (LED::Red);
 		b->second->set_state (LED::OneShot24th);
 		break;