…e OP_ENTERITER and not OP_ITER

…cals

Rather than generating an entire temporary list that is twice as big as
the original array, instead set a flag on the `OP_ITER` that tells it to
set one of the iteration variables to the current array index and use
the same `CXt_LOOP_ARY` optimisation that regular foreach over an array
would use.

…op.c can take its address