Ticket History #6785: Add gss_krb5_import_cred

Add gss_krb5_import_cred from Heimdal; allows krb5 creds to be
acquired from a keytab or ccache into a GSSAPI credential without
using global process or thread variables.

Merged from the users/lhoward/import-cred branch.


https://github.com/krb5/krb5/commit/e76d9a48c905e6db8ea9b7af4b843070756effaa
Commit By: ghudson
Revision: 24356
Changed Files:
U trunk/src/lib/gssapi/generic/gssapi_ext.h
U trunk/src/lib/gssapi/krb5/acquire_cred.c
U trunk/src/lib/gssapi/krb5/copy_ccache.c
U trunk/src/lib/gssapi/krb5/gssapiP_krb5.h
U trunk/src/lib/gssapi/krb5/gssapi_krb5.c
U trunk/src/lib/gssapi/krb5/gssapi_krb5.hin
U trunk/src/lib/gssapi/krb5/krb5_gss_glue.c
U trunk/src/lib/gssapi/krb5/set_allowable_enctypes.c
U trunk/src/lib/gssapi/libgssapi_krb5.exports
U trunk/src/lib/gssapi/mechglue/g_set_cred_option.c
U trunk/src/lib/gssapi/mechglue/mglueP.h
U trunk/src/lib/gssapi/spnego/gssapiP_spnego.h
U trunk/src/lib/gssapi/spnego/spnego_mech.c
U trunk/src/lib/krb5/libkrb5.exports
U trunk/src/tests/gssapi/t_gssexts.c