previously removed after visiting:
  This could lead to visiting the same subgraph more than once (and
  quadratic runtime), but is not neccessary:
  If a subgraph was once visited, all addresses were already added to
  the set of "free" nodes.
  This fixes the mostly endless runs of the compiler for big methods,
  for instance in 176.gcc/calls.c after running cond_eval.c once more
- BugFix: add missing call to new initializer handling
- BugFix: if a node is exchanged, use the new node (not the Id) for
  further checks
- simplified the code
- fixed indentation

[r19652]