On the fsfs-format7 branch: Fix off-by-one error when
reading negative values from packed_data streams.

* subversion/libsvn_subr/packed_data.c
  (svn_packed__data_fill_buffer): turn + into -

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsfs-format7@1467362 13f79535-47bb-0310-9956-ffa450edef68