Herlihy-Wing queue example (involving prophecy variables)

See merge request iris/examples!25

generalized rdcss to arbitrary (unboxed) values

See merge request !23

For the expected value at the A location we require that it is unboxed and for the expected value n1 at the B location we require that [InjLV n1] is unboxed.

Add erasure

See merge request !22

Also needs a new token and splitting ownership of the "main" protocol location.