Add collection support for KEYRING ccache type

Add collection support for KEYRING ccache type

Augment the KEYRING ccache type to support collection semantics
similar to those of the DIR type.  For keyrings with no anchor prefix,
maintain compatibility with old code by linking the initial primary
cache directly from the session keyring and naming it after the
collection.

See http://k5wiki.kerberos.org/wiki/Projects/Keyring_collection_cache
for more information.  Adapted from a patch by simo@redhat.com.

ticket: 7711 (new)