Podcast and librivox plugins are broken (can not add tracks to playlist)

Rev 3667, when double-clicking a podcast:

Traceback (most recent call last):
  File "/home/steve/exaile/plugins/podcasts/__init__.py", line 175, in _parse_podcast
    pl.add_tracks(tracks)
AttributeError: 'Playlist' object has no attribute 'add_tracks'

Traceback (most recent call last):
  File "/home/steve/exaile/plugins/librivox/__init__.py", line 190, in on_append_to_playlist
    self.add_to_playlist([chapter], location=None)
  File "/home/steve/exaile/plugins/librivox/__init__.py", line 195, in add_to_playlist
    current_playlist.add_tracks(tracks, location)
AttributeError: 'Playlist' object has no attribute 'add_tracks'