Make 'svnauth' show the path to the configuration area used, and the number
of credentials matched during listing/deletion. And raise an error if no
credentials were matched to make it easier for scripts to tell whether
listing/deletion succeeded.

* subversion/svnauth/svnauth.c
  (walk_credentials_baton_t): Add 'matches' counter.
  (walk_credentials): Increment 'matches' counter for each matched credential.
  (subcommand_list, subcommand_delete): Initialise 'matches' counter to zero
   and print information based on it when the operation is done.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1521491 13f79535-47bb-0310-9956-ffa450edef68