Handle edits while playing precisely.

This avoids stuck notes if active notes are edited, but without stopping all
active notes in the region on any edit as before.

This implementation injects note ons in places that aren't actually note
starts.  Depending on how percussive the instrument is, this may not be
desired.  In the future, an option for this would be an improvement, but there
are other places where "start notes in the middle" is a reasonable option.  I
think that should be handled universally if we're to do it at all, so not
considering it a part of this fix for now.

libs/evoral/src/Event.cpp

@@ -63,6 +63,22 @@ Event<Timestamp>::Event(EventType type, Timestamp time, uint32_t size, uint8_t*
 	}
 }
 
+template<typename Timestamp>
+Event<Timestamp>::Event(EventType      type,
+                        Timestamp      time,
+                        uint32_t       size,
+                        const uint8_t* buf)
+	: _type(type)
+	, _original_time(time)
+	, _nominal_time(time)
+	, _size(size)
+	, _buf((uint8_t*)malloc(size))
+	, _id(-1)
+	, _owns_buf(true)
+{
+	memcpy(_buf, buf, _size);
+}
+
 template<typename Timestamp>
 Event<Timestamp>::Event(const Event& copy, bool owns_buf)
 	: _type(copy._type)