Support FAST hide-client-names option

In the KDC, if we see the hide-client-names option, identify the
client as the anonymous principal in KDC-REP and KRB-ERROR responses.
The actual client name is present in encrypted FAST elements.

ticket: 7700 (new)
Fix FAST critical option bit checking

The FAST option bits 0-15 are intended to be critical--if they are
present and a KDC does not support them, the KDC is supposed to fail
the request.  Because of an incorrect constant, we were erroneously
recognizing bits 24-31 as critical.  Fix the constant.

ticket: 7701 (new)