Compute fixed points for loops

[hermanventer]

If the behavior of a loop can be nicely summarized as a set of unknown properties on known objects, the the effects of the loop on the heap is known and it will be safe to emit a residual loop into the code at the point of time associated with the loop. This will do two nice things:

1. Keep a compact representation of the code by not unrolling loops.
2. Allow us to deal with loops with unknown bounds.