On the fsfs-format7 branch:  When serializing signed / deltified 64 bit
integers, make sure we use the full value range.  Otherwise, some values
cannot be represented.

* subversion/libsvn_subr/packed_data.c
  (svn_packed__data_flush_buffer,
   svn_packed__data_fill_buffer): map -1 to 1, -2 to 3 etc. instead of
                                  starting at 3.

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsfs-format7@1469487 13f79535-47bb-0310-9956-ffa450edef68