Description: Extend class notation to include indexed intersection. Note:
Historically (prior to 21-Oct-2005), set.mm used the notation
|^| x e. A B , with the same intersection symbol as cint . Although
that syntax was unambiguous, it did not allow for LALR parsing of the
syntax constructions in set.mm. The new syntax uses a distinguished
symbol |^|_ instead of |^| and does allow LALR parsing. Thanks to
Peter Backes for suggesting this change.