3425
3426 - clear trace analysis cruft

Now we have a record we can do the rest off version control.
3427 - support overflowing bounds in slices

http://arclanguage.org/item?id=18451

This slight reorg caused enq/deq to break because they were
unintentionally overriding 'len which they now suddenly found themselves
needing to call. First time I've regretted the lisp-1 design decision.