Make the skip handling in the repos_diff code more explicit, by just
skipping what we document as to be skipped. This makes more of the merge
skipping code self documenting.

* subversion/libsvn_client/merge.c
  (merge_dir_added,
   merge_dir_opened): Request skipping children for tree conflict.

* subversion/libsvn_client/repos_diff.c
  (delete_entry,
   add_directory,
   open_directory,
   add_file,
   open_file,
   close_directory): Only automatically skip children of parent if we should,
     instead of also for tree conflicts and on some cases where the node itself
     is skipped. Note that this is just an internal api.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1433597 13f79535-47bb-0310-9956-ffa450edef68