code: private int endCheckBreak()
      {
          Node n = ((Jump) this).getJumpStatement();
          n.putIntProp(CONTROL_BLOCK_PROP, END_DROPS_OFF);
          return END_UNREACHED;
      }
docs: When a break is encountered annotate the statement being broken
  out of by setting its CONTROL_BLOCK_PROP property.
  @return logical OR of END_* flags