Add rxgk_token.c
Routines for constructing tokens (both regular and printed), extracting
and decrypting tokens, and helpers therein.
Provide the ability to print a token using a given session key and
using a random session key; the former is useful for certain variants
of localauth wherein a dummy GSS negotiation is performed with the
same identity acting as initiator and acceptor.
Include a paranoid sanity-check that only the routines intended to
produce printed tokens can produce tokens with a zero-length identities
list.
Change-Id: I0cde7fd0cdf9a27777523cd502b21bdccef41dcc
Reviewed-on: https://gerrit.openafs.org/10567
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>