o Minor bugfixes (defensive programming, undefined behavior):

    - Fix a memset() off the end of an array when packing cells.  This
      bug should be harmless in practice, since the corrupted bytes
      are still in the same structure, and are always padding bytes,
      ignored, or immediately overwritten, depending on compiler
      behavior. Nevertheless, because the memset()'s purpose is to
      make sure that any other cell-handling bugs can't expose bytes
      to the network, we need to fix it. Fixes bug 22737; bugfix on
      0.2.4.11-alpha. Fixes CID 1401591.