Build 3961 library in userspace, and add enctypes

Build the 3961 library in userspace, with support for the common
kerberos enctypes des3-hmac-sha1, arcfour-hmac-md5, and aesXXX-cts-hmac-sha1-96.
Export new symbols as well, and suppress deprecated warnings.

Rename all symbols, both exported and not, with an oafs_h_ prefix
so as to reduce the chance of conflicts.

Rename heim_octet_string to avoid confusion about where things are coming
from.

Change-Id: If5155661deb5adf73329eb8b90021512c01a290f
Reviewed-on: http://gerrit.openafs.org/10050
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>