TODO
****

   * NSZone memory allocation may not work correctly. If you encounter
     a problem with NSZones, switch to using the default zone instead
     of creating one.

   * Invocations (and by extension, Distributed Objects) work well only
     on ix86 platforms. In particular, they don't work well on PPC and
     Sparc platforms.

   * Distributed Objects aren't thread safe. Don't use DO between
     threads in a multi-theaded app.