get_maintainer.pl: add support for moderated lists

Currently get_maintainer.pl reports moderated lists as open, which is just
wrong.

Signed-off-by: Richard Weinberger <richard@nod.at>
Acked-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>