Time: tztime: mention IANA TZ Database in help

https://www.iana.org/time-zones uses the spelling IANA Time Zone Database,
so I use it too.
Time: update messages.pot & l10n-fi

I translated IANA Time Zone Database too, because I tried googling for
my translation and the first results are about correct thing (even if
Google first suggests wrong spelling which (when clicked) suggests two
other wrong spellings…

[SKIP CI]
Internet: Make @dns show all addresses. Closes GH-786.
Internet: Remove duplicate IPs from @dns.
Internet: override reply.oneToOne and always send IPs in one message (there are potentially a lot of them).
src/irclib.py: remove some errors