Where a merge throws an error to report that there were conflicts, move
that code up to the calling function, one small step closer to making it
available through the API.  For issue #4316 "Merge errors out after
resolving conflicts".

* subversion/libsvn_client/merge.c
  (make_merge_conflict_error): Remove an unused parameter.
  (merge_locked,
   merge_reintegrate_locked,
   merge_peg_locked,
   do_automatic_merge_locked): Report conflicts through an output parameter
    instead of by an error. Add a 'result_pool' parameter.
  (svn_client_merge5,
   svn_client_merge_reintegrate,
   svn_client_merge_peg5,
   svn_client_do_automatic_merge): Call make_merge_conflict_error() here
    instead.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1446605 13f79535-47bb-0310-9956-ffa450edef68