make some symbols public

[Bjoern JACKE]

Hi,

it would be good if some symbols, which are private at the moment 
would be make public as Samba uses them:

decode_krb5_ap_req()
error_message()
krb5_set_default_tgs_ktypes()
initialize_krb5_error_table()
krb5_locate_kdc()

Thanks
Bjoern