The main changes are:
- Do not create a branch table entry for unreachable code. This saves space and permits a uniform
  treatment of branches.
- Use the correct stack length for the Loop branch target (we're taking the branch before being in
  the label, so the current stack needs to be added).
- Take the Else source and target branches at the correct time (i.e. when the stack is the expected
  one such that the stack length is correctly computed).