Try a little harder to avoid returning e-text that says "Generic error (see

Try a little harder to avoid returning e-text that says "Generic error (see
e-text)" for out-of-range codes where we haven't explicitly decided to return a
vague error message.

* do_as_req.c (prepare_error_as): New argument, the error message text as
determined *before* possibly replacing the error code with "generic error".
(process_as_req): Fill it in based on 'status', or the error message
corresponding to the error code to be returned.
* do_tgs_req.c (prepare_error_tgs): New argument, the error message text as
determined *before* possibly replacing the error code with "generic error".
(process_tgs_req): Fill it in based on 'status', or the error message
corresponding to the error code to be returned.

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@14835 dc483132-0cff-0310-8789-dd5450dbe970