cvsserver: make the output of 'update' more compatible with cvs.

cvsserver: make the output of 'update' more compatible with cvs.

Native cvs update outputs the string "cvs update: Updating <DIR>" for
every directory it processes (to stderr) unless -q or -Q is given on
comman-line. This is used, e.g., by emacs pcl-cvs to split files by
directory. This commit implements this feature in cvsserver.

Signed-off-by: Sergei Organov <osv@javad.com>
Acked-by: Martin Langhoff <martin.langhoff@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>