parsecvs maintenance was taken over by ESR, and the name
changed to cvs-fast-export as it learned to support that
output format. Let's point to cvs-fast-export, as it should
have additional bug-fixes and be more convenient to use.
Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>