Added two new routines for multiple encryption type support:

Added two new routines for multiple encryption type support:
   krb5_set_default_tgs_ktypes(context, ktypes)
	This routine sets the default application session key types to be used.
   krb5_get_tgs_ktypes(context, principal, &ktypes)
	This routine gets the session key types to be used with "principal".
	At the moment, this only uses the krb5_set_default_tgs_ktypes values
	or those specified in libdefaults/default_tgs_enctypes (krb5.conf).
	It is envisioned that this may later support per-host/per-realm lookup.

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@7168 dc483132-0cff-0310-8789-dd5450dbe970