memory_summary - return a summary of memory usage

mapping memory_summary();

memory_summary() returns a mapping of the form:

PRE(
([ 
  program name : ([
    var name : mem usage,
    ...
  ])
  ...
])
)

the memory usage is the memory required to store the value divided by the
number of variables pointing to that particular value.  [Due to sharing
of values, giving an exact number for the memory usage of any
value is impossible]

This efun is only available if PACKAGE_CONTRIB is defined.

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