* subversion/include/svn_client.h
  (SVN_CLIENT_COMMIT_ITEM_LOCK_TOKEN): Document.

Found by: brane
Suggested by: rhuijben

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1468109 13f79535-47bb-0310-9956-ffa450edef68