Prepare for distinct live-midi event type

The motivation for this is to determine if a given event
originates from a user-controlled live input controller or
from playback from disk or a MIDI file.

This distinction is required for VST3 MIDI learn.

libs/ardour/luabindings.cc

@@ -620,6 +620,12 @@ LuaBindings::common (lua_State* L)
 		.addConst ("Curved", Evoral::ControlList::InterpolationStyle(Evoral::ControlList::Curved))
 		.endNamespace ()
 
+		.beginNamespace ("EventType")
+		.addConst ("NO_EVENT", Evoral::EventType(Evoral::NO_EVENT))
+		.addConst ("MIDI_EVENT", Evoral::EventType(Evoral::MIDI_EVENT))
+		.addConst ("LIVE_MIDI_EVENT", Evoral::EventType(Evoral::LIVE_MIDI_EVENT))
+		.endNamespace ()
+
 		.endNamespace (); // Evoral
 
 	luabridge::getGlobalNamespace (L)

libs/evoral/evoral/Event.h

@@ -123,6 +123,9 @@ public:
 	inline const uint8_t* buffer()        const { return _buf; }
 	inline uint8_t*       buffer()              { return _buf; }
 
+	inline bool           is_midi ()      const { return _type == LIVE_MIDI_EVENT || _type == MIDI_EVENT; }
+	inline bool           is_live_midi () const { return _type == LIVE_MIDI_EVENT; }
+
 	inline void set_event_type(EventType t) { _type = t; }
 
 	inline void set_time(Time t) { _time = t; }

libs/evoral/evoral/types.h

@@ -51,7 +51,8 @@ typedef int32_t event_id_t;
  */
 enum EventType {
 	NO_EVENT,
-	MIDI_EVENT
+	MIDI_EVENT,
+	LIVE_MIDI_EVENT
 };
 
 /** Type of a parameter (opaque, mapped by application, e.g. gain) */