mailinfo: do not get confused with logical lines that are too long.

mailinfo: do not get confused with logical lines that are too long.

It basically considers all the continuation lines to be lines of their
own, and if the total line is bigger than what we can fit in it, we just
truncate the result rather than stop in the middle and then get confused
when we try to parse the "next" line (which is just the remainder of the
first line).

[jc: added test, and tightened boundary a bit per list discussion.]

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>