On the fsx-branch:  Rename svn__priority_queue_* API elements
to svn_priority_queue__*.

* subversion/include/svn_sorts.h
  (svn__priority_queue_*): rename to ...
  (svn_priority_queue__*): ... this

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

* subversion/libsvn_fs_x/pack.c
  (write_l2p_index): update API user

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsx@1508122 13f79535-47bb-0310-9956-ffa450edef68