Use pixbufs as region name labels rather than Gnome::Canvas::Text. Don't set height...

Use pixbufs as region name labels rather than Gnome::Canvas::Text. Don't set height on every regionview in non-stacked mode in StreamView::add_region_view (speeds up some playlist operations).

git-svn-id: svn://localhost/ardour2/branches/3.0@5071 d708f5d6-7413-0410-9779-e7cbd77b26cf