TODO
****

   * Some people have reported NSZone memory allocation problems.  If
     you encounter a problem with NSZones, switch to using the default
     zone instead of creating one. Or better yet, fix the problem and
     submit a patch.

   * Invocations (and by extension, Distributed Objects) have been well
     tested only on ix86 platforms. In particular, there are still
     minor problems on PPC and Sparc platforms.

   * Distributed Objects is now thread safe, but it hasn't been well
     tested.