On the fsx-branch:  Rename svn__prefix_string_* API elements
to svn_prefix_string__*.

* subversion/include/private/svn_string_private.h
  (svn__prefix_string_*): rename to ...
  (svn_prefix_string__*): ... this

* subversion/libsvn_subr/prefix_string.c
  (): ditto.

* subversion/libsvn_fs_x/pack.c
  (path_order_t,
   copy_node_to_temp,
   compare_path_order): update user


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsx@1508120 13f79535-47bb-0310-9956-ffa450edef68