Whoops: the rip hash function is supposed to ignore the is_private
field so that it can be used with rips_equal_modulo_privateness.  Make
it so.
Extend ft2 so that it can read in a types file at the start and extend
it as it works.
Add in some gubbins so that we can do periodic work while ft2 is running.
Support for periodically dumping the database which we've collected so
far, so that I can plot nice graphs of the convergence rates.
Arrange that FT2 only logs stuff relevant to the main binary, since
that's the only bit we care about when we actually use the table.
Without this, the snapshotting stuff is just too slow to be useful.
Whoops: make sure that the snapshots only include the things which
we've actually used so far, and not the slop space.