DB backend support for lmdb?

[Steffen Nurpmeso]

Hello.

Matthias Andree wrote in <9a51593a-a5ce-06f3-6070-af25b1a6db34 at an3e.de>:
 |Am 18.07.2018 um 01:19 schrieb Matthias Andree:
 |> Before doing further development, please switch to
 |> ^/branches/lmdb-support and/or update. I'm heading for bed now that
 |> r7064 has been committed.
 |
 |...make that r7065.

All tests pass for me now.

- I had a failure still in db_foreach(), which caused t.encoding
  to fail.  (That was a leftover from the first implementation
  idea, which toggled in between "master" and "txn".)
- I have given up setting an initial size unless that is for the
  fixed-size implementation, but which is not the default.
- I have not yet catched the "other process caused resize" error
  (again), now we do that.
- In order to comply with bogofilter's "newly-created" paradigm we
  now use two named databases, one for the data, the other's use
  is just to be existent, or not, used as the indicator.

I hope this is satisfying.
I will attach the entire new source.

Ciao!  And thanks for bogofilter.

--steffen
|
|Der Kragenbaer,                The moon bear,
|der holt sich munter           he cheerfully and one by one
|einen nach dem anderen runter  wa.ks himself off
|(By Robert Gernhardt)