add latest iana timezones

this makes it possible to set the timezone by setting TZ env var
to something like Europe/Berlin, optimally from /etc/profile,
or ~/.profile.

in order to use those timezone files on musl, the latest
timezone fixes from musl git must be pulled (for example by installing
musl-git package).
additionally there's still a bug in musl's __map_file() which uses
O_NOFOLLOW when opening timezone data files, which prevents our
symlinks from working currently. this will probably be fixed soon
as well.

what already works correctly is to set the TZ via the timezone string
at the end of those timezone files, for example:
TZ="CET-1CEST,M3.5.0,M10.5.0/3" (this would be the setting for
Europe/Berlin).