Add a -L option to wc(1), for finger compatibility with the GNU
wc utility. The -L option can be used to report the length of
the longest line wc has seen in one or more files. It is
disabled by default, and wc uses the standard `-lwc'.

Submitted by: Sheldon Givens, sheldon at sigsegv.ca
Reviewed by: kib
MFC after: 1 week