NoteBase-derived note objects must delete their children, because
often they are deleted long before the parent (group) is. However,
in MidiView::clear_events() we used to call _note_group->clear (true)
first, which would delete the canvas items owned by these objects,
without them knowing about it. This made it dangerous for them
to delete those same items in their destructors.
This reverses the ordering so that NoteBase objects are deleted first
(along with their canvas items) and after that we clear _note_group
which will address any danging canvas items created there that are
not owned by a NoteBase-derived object
This is mostly a simple lexical search+replace but the absence of operator< for
std::weak_ptr<T> leads to some complications, particularly with Evoral::Sequence
and ExportPortChannel.
Copyright-holder and year information is extracted from git log.
git history begins in 2005. So (C) from 1998..2005 is lost. Also some
(C) assignment of commits where the committer didn't use --author.
