Open 1.8.x backport branch for r1561426.

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.8.x-r1561426@1561547 13f79535-47bb-0310-9956-ffa450edef68
On the 1.8.x-r1561426 branch:
Merge r1561426 from /trunk, resolve the conflict and adapt code where necessary.

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.8.x-r1561426@1561549 13f79535-47bb-0310-9956-ffa450edef68
Merge the 1.8.x-r1561426 branch:

 * r1561426
   In FSFS, skip the generation of uniquifiers if rep-shared is not supported.
   Branch: ^/subversion/branches/1.8.x-r1561426
   Justification:
     This is not known to be a bug, atm, as we omit these when we write the
     final revisions.  But we rely on those uniquifiers to be NULL in old
     repo formats when we compare reps.  Them being non-NULL in a txn might
     cause problems with future changes.
   Votes:
     +1: stefan2, breser, rhuijben


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.8.x@1640481 13f79535-47bb-0310-9956-ffa450edef68
Merge r1636874 from trunk:

 * r1636874
   Provide @since information in svn_stream_skip docstring.
   Justification:
     Our API docs should be accurate.
   Votes:
     +1: stefan2, julianfoad, rhuijben


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.8.x@1640483 13f79535-47bb-0310-9956-ffa450edef68
* STATUS: Update r1536854 entry.

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.8.x@1640563 13f79535-47bb-0310-9956-ffa450edef68
* STATUS: Approve r1589360.

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.8.x@1640565 13f79535-47bb-0310-9956-ffa450edef68