Add krb5_free_context stub to rfc3961

Change-Id: I5df22e74ea9a5a057994b6684a09eb0f03da98d2
Reviewed-on: http://gerrit.openafs.org/10048
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Simon Wilkinson <simonxwilkinson@gmail.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Disable some heimdal bits

For the rfc3961 library, we don't want linker exposure to an
entropy-gathering daemon, and we don't want to be leaving entropy
seed files around in user homedirs.

Change-Id: I54546ad44fcdfac8227e72b68a33fa4f61df50b0
Reviewed-on: http://gerrit.openafs.org/10049
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Simon Wilkinson <simonxwilkinson@gmail.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>