Ticket History #6958: Make gss-krb5 use cache collection

For default credentials, defer ccache resolution until we need the
information. If this happens in init_sec_context when we have the
target principal in hand, use krb5_cc_select() to pick a cache. If
the target principal is not known, use the default cache.

For credentials with a specified principal, use krb5_cc_cache_match()
to find the cache. If no cache is found and a password is specified,
create a new cache within the collection to hold the new credentials,
if the default cache type supports a collection.

https://github.com/krb5/krb5/commit/1cd2821c19b2b95e39d5fc2f451a035585a40fa5
Commit By: ghudson
Revision: 25160
Changed Files:
U trunk/src/lib/gssapi/krb5/acquire_cred.c
U trunk/src/lib/gssapi/krb5/gssapiP_krb5.h
U trunk/src/lib/gssapi/krb5/iakerb.c
U trunk/src/lib/gssapi/krb5/init_sec_context.c
U trunk/src/lib/gssapi/krb5/inq_cred.c
U trunk/src/lib/gssapi/krb5/s4u_gss_glue.c
U trunk/src/tests/gssapi/Makefile.in
U trunk/src/tests/gssapi/deps
A trunk/src/tests/gssapi/t_ccselect.c
A trunk/src/tests/gssapi/t_ccselect.py