mdbx and lmdb related fixes.

badger: ReplaceEvent()

replacer and lmdb migration to fix pathological duplicates.

Merge branch 'hyperloglog'

ok, this is a bug we already had: if an event matches two different t…

badger/lmdb: make negentropy work better and guard against giant make…

badger: update ristretto so it doesn't conflict with other stuff.

badger: remove two broken Next() calls.

badger: ok, now BadgerBackend has to be passed as a pointer everywhere.

lmdb: hotfix for leaked goroutine.