Add -A (require authentication but not necessarily authorization) and

Add -A (require authentication but not necessarily authorization) and
-C (user wants local credentials) flags to ftpd.

If -C is set, write out forwarded credentials to disk and use krb524 to
get krb4 tickets as well. If user doesn't forward credentials, require
a password even if auth was successful and use that to get credentials.

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@10993 dc483132-0cff-0310-8789-dd5450dbe970