Automatic flushing of the jnl files

[Tony Finch]

I got annoyed by having to manually tune max-journal-size so I had a hack
at the problem:

https://git.csx.cam.ac.uk/x/ucs/ipreg/bind9.git/commitdiff/c8f083b797f9810f

Tony.
-- 
f.anthony.n.finch  <dot at dotat.at>  http://dotat.at/
Viking: Southeast, veering south or southwest later, 4 or 5, increasing 6 at
times. Moderate or rough. Wintry showers. Good, occasionally poor.