- set() handles overflow as max_value() - the principle of least surprise.
- use pointers in iterator to avoid any assignment issues. Allows default
  bitwise copy/assignment.

- added Mattijs' speed tests
- optimized resize() and assignment operators to avoid set() method
- add const_iterator and re-did the proxy handling.

Reading/writing by looping across iterators is still somewhat slow, but
might be acceptable.

largest and smallest representable values.  Accessible directly and via pTraits.

- eliminated previous PackedBitRef class, the iterator does all of that and
  can also be used to (forward) traverse the list
- no const_iterator yet

- Note that PackedList is also a bit like DynamicList in terms of storage
  management and the append() method. Since the underlying storage in
  integer, any auto-vivified elements will also flood-fill the gaps with
  zero.

- removed Cmu from kOmegaSST models - not used
- general tidying up

- new members:  capacity(), two-argument resize()/setSize(), const storage()
- new static members: max_value(), packing(), etc.

- added STL-compatible resize() method.
  Should this be the primary entry point?

- made [DS]LListBase end iterators private