A minor automatic merge optimization.

* subversion/libsvn_client/merge.c:

  (source_and_target_t): Remove source_mergeinfo and target_mergeinfo
   members, they are no longer referenced.

  (find_automatic_merge): Don't populate the defunct members of
   source_and_target_t.  This saves us one or two round-trips asking for
   mergeinfo from the repos.



git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1464199 13f79535-47bb-0310-9956-ffa450edef68