On the fsfs-improvements branch:  Fix FSX build by enabling the
dir_optimal_order vtable entry.

* subversion/libsvn_fs_x/tree.c
  (root_vtable): uncomment said entry

Found by: philip

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsfs-improvements@1511145 13f79535-47bb-0310-9956-ffa450edef68