On the fsfs-format7 branch:  Refine our block stuffing strategy during
pack() to minimize the reads that span more than one block.

* subversion/libsvn_fs_fs/pack.c
  (select_block_entries): don't place parsed items near the end of the block;
                          replace large items overlapping the block boundary
                          with smaller ones from the next block


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsfs-format7@1476661 13f79535-47bb-0310-9956-ffa450edef68