LFUN
  void RemoveExtraEntry (mixed name, mixed prop)

DESCRIPTION
  Remove data from this objects P_EXTRA_DESC.

  Arguments:
    name: the key value to remove data from.
    prop: the field name to remove.

  The entry P_EXTRA_DESC[<key>][<prop>] and thus the data stored there
  is removed.

EXAMPLE
  RemoveExtra("my data", P_SHORT);

IMPLEMENTED
  /std/thing/description