when receiving unexpected hook, print the value
even though we check in parse.y, lets avoid a possible null deref
Implement a simple envelope cache. The caching strategy is very simple
for now. Every new and updated envelopes are cached.  The cache size
is limited, so cached envelopes are put in a FIFO queue. If the cache
size is reached, the oldest (least recently updated) cached envelopes
is dropped to make room.
Merge branch 'master' of ssh://ssh.poolp.org/git/opensmtpd