Fix a bug in libsvn_client, uncovered by work on WC-NG.
Fix a bug in libsvn_client, uncovered by work on WC-NG.

* subversion/libsvn_client/commit_util.c
  (harvest_committables): Make the code match the comments by ensuring that
    used_url is always set.  Add a note about WC-NG to the comment.


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@876343 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion