Changed GSSAPI opaque types (gss_name_t, gss_cred_id_t, gss_ctx_id_t) from

Changed GSSAPI opaque types (gss_name_t, gss_cred_id_t, gss_ctx_id_t) from
void* to pointers to opaque structs.  This change removed some casts and
introduced or changed a bunch of other casts to suppress warnings.

krb5_gss_accept_sec_context(): Fixed a bug found by the above changes
where krb5_gss_release_cred() was being called with the wrong argument 2
(gss_cred_id_t instead of gss_cred_id_t*).

ticket: 4057
status: open

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@18396 dc483132-0cff-0310-8789-dd5450dbe970