[krbdev.mit.edu #6848] gss library minor status codes are not exposed

[Arlene Berry via RT]

None of the minor status codes returned by the gss library itself are
defined in installed header files.  These codes include the ones defined
by src/lib/gssapi/generic/gssapi_err_generic.et and
src/lib/gssapi/krb5/gssapi_err_krb5.et and 5 ERR_SPNEGO codes defined in
src/gssapi/spnego/gssapiP_spnego.h.  We need to check for one of these
codes.  I would provide a patch but I'm not certain how you would prefer
to solve this.