Efuns for general LPC values

These efuns act on arbitrary values of various types.

<DL>
*  copy
*  fetch_variable
*  filter
*  map
*  restore_variable
*  save_variable
*  store_variable
*  sizeof
*  typeof
*  undefinedp
</DL>

 Tim Hollebeek  Beek@ZorkMUD, Lima Bean, IdeaExchange, and elsewhere