* Updated the maximum length of RSS <channel> entries to match
the current DB schema in the 'Edit Feed' dialog in rdadmin(1).
* Added a 'FEEDS.CHANNEL_EDITOR' field to the database.
* Incremented the database version to 318.
* Added 'RDFeed::channelEditor()' and
'RDFeed::setChannelEditor()' methods.
* Added an 'Editor' control to the 'Channel' controls in the
'Edit Feed' dialog in rdadmin(1).