Reorder displayed names of thread authors

Reorder displayed names of thread authors

When displaying threads as result of a search it makes sense to list those
authors first who match the search. The matching authors are separated from the
non-matching ones with a '|' instead of a ','

Imagine the default "+inbox" query. Those mails in the thread that
match the query are actually "new" (whatever that means). And some
people seem to think that it would be much better to see those author
names first. For example, imagine a long and drawn out thread that once
was started by me; you have long read the older part of the thread and
removed the inbox tag. Whenever a new email comes in on this thread,
prior to this patch the author column in the search display will first show
"Dirk Hohndel" - I think it should first show the actual author(s) of the new
mail(s).

Signed-off-by: Dirk Hohndel <hohndel@infradead.org>