Add ksu option for non-forwardable tickets

Add ksu -F and -P options to explicitly not request forwardable and
proxiable tickets.

https://github.com/krb5/krb5/commit/0e4932982665c69cc4417eb7dbf0eda87fe5bd3e
Author: Greg Hudson <ghudson@mit.edu>
Commit: 0e4932982665c69cc4417eb7dbf0eda87fe5bd3e
Branch: master
 doc/user/user_commands/ksu.rst |   15 +++++++++++++--
 src/clients/ksu/main.c         |   11 +++++++++--
 2 files changed, 22 insertions(+), 4 deletions(-)