Merge Luke's users/lhoward/heimmig branch to trunk.  Implements a
KDC back-end plugin which interfaces to a Heimdal HDB plugin.


https://github.com/krb5/krb5/commit/2a5ccaf5a2456e8cfc3f774df307386404bfbec3
Commit By: ghudson
Revision: 23073
Changed Files:
U   trunk/src/configure.in
U   trunk/src/include/kdb_ext.h
U   trunk/src/include/krb5/authdata_plugin.h
U   trunk/src/kdc/do_as_req.c
U   trunk/src/kdc/do_tgs_req.c
U   trunk/src/kdc/kdc_authdata.c
U   trunk/src/kdc/kdc_util.c
U   trunk/src/kdc/kdc_util.h
U   trunk/src/kdc/policy.c
U   trunk/src/lib/kadm5/srv/svr_principal.c
U   trunk/src/lib/kdb/kdb5.c
U   trunk/src/lib/kdb/libkdb5.exports
U   trunk/src/plugins/authdata/greet_server/greet_auth.c
A   trunk/src/plugins/kdb/hdb/