Re-tweak maintainer-mode stack traces error code printing: when you have
"Ditto" to say, say nothing.

* subversion/libsvn_subr/error.c
  (print_error): Omit "ditto" error code information.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1467450 13f79535-47bb-0310-9956-ffa450edef68