In the locking code: Obtain url of BASE node, existing lock and revision with
just a single database operation.

* subversion/libsvn_client/locking_commands.c
  (wc_lock_item_t): New struct.
  (organize_lock_targets): Use wc_ctx argument. Build hash in first loop and
    use result later.
  (svn_client_lock,
   svn_client_unlock): Update caller.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1442652 13f79535-47bb-0310-9956-ffa450edef68