heimdal: Add parameter to windc_plugin to allow extended return codes.

heimdal: Add parameter to windc_plugin to allow extended return codes.

These changes add a krb5_data parameter named e_data to the windc_plugin to
allow the samba KDC to return extended error information in addition to the
standard KRB5KDC_ERR_* codes.  Windows uses the extended information to provide
detailed information in user dialogs (e.g. account disabled, logon hours
restriction, must change password, etc.).

This particular commit modifies only heimdal code.  Hopefully this can be
submitted and accepted into the upstream heimdal codebase.