Create a new class, FileDataCollector, to serve as an RCS parser Sink.

Create a new class, FileDataCollector, to serve as an RCS parser Sink.

Instead of the CollectData class serving as the Sink, use a new
instance of FileDataCollector for each file that needs to be parsed.

* cvs2svn (FileDataCollector): New class.  Most of its contents are
  taken directly from the CollectData class.

  (CollectData): Don't implement cvs2svn.rcsparse.Sink anymore.
  Removed methods from that interface.

  (CollectData.get_file_data_collector): Return an instance of
  FileDataCollector (instead of self).

git-svn-id: http://cvs2svn.tigris.org/svn/cvs2svn/trunk@1807 be7e6eca-30d4-0310-a8e5-ac0d63af7087