On the fsfs-format7 branch: make svn_stream__from_spillbuf accept an
existing spill-buffer instead of creating one internally.  Update callers.

* subversion/include/private/svn_subr_private.h
  (svn_stream__from_spillbuf): use existing spillbuf
* subversion/libsvn_subr/spillbuf.c
  (svn_spillbuf_reader_t): embed spill-buffer via pointer to allow using
   existing ones
  (svn_spillbuf__reader_create,
  (svn_spillbuf__reader_read,
  (svn_spillbuf__reader_write): update
  (svn_stream__from_spillbuf): implement API change

* subversion/libsvn_fs_base/lock.c
  (svn_fs_base__get_locks): update caller
* subversion/libsvn_subr/stream.c
  (svn_stream_buffered): ditto
* subversion/tests/libsvn_subr/spillbuf-test.c
  (test_spillbuf_stream): same here


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsfs-format7@1430673 13f79535-47bb-0310-9956-ffa450edef68