lzmainfo has had translation support since 2009 at least but
it was never added to po/POTFILES.in so the messages weren't
translated. It's a very rarely needed tool so it's not too bad.
This also adds src/xz/mytime.c to po/POTFILES.in although there
are no translatable strings. It's simpler this way so that it
won't be forgotten if strings were ever added to that file.
6d35fcb936