Fix a memory usage inefficiency in the FSFS svn_fs_history_t construction
code as well as an inconsistency therein.

* subversion/libsvn_fs_fs/tree.c
  (fs_node_history,
   history_prev): No need to normalize (and implicitly duplicate) the
                  path parameters here because we do that already in ...
  (assemble_history): Duplicate PATH_HINT as well and update the docstring
                      now saying that we duplicate all data that needs to
                      be persistent.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1590385 13f79535-47bb-0310-9956-ffa450edef68