- This should fix some cases where we would not reassociate constants
  because of multiple users and missed address mode patterns for these
  cases.

This also allows to cleanup the finish neg/add carry flag fix code a
big.

- For equal destinations merge the switch table entries and Proj nodes
- Handle Switches with just a default Proj like Jmp nodes

- Normalize switch table now (sort + remove default entries)
- Correctly handle the case of multiple entries mapping to the same proj
  number.

- No strange split between no-phi and phi variants anymore. The phi
  variant can perform everything now.
- Repeat till we reach the fixpoint.

The were some comments in the code indicating that in case of SSA
destruction problems critical edges were not created. But we deal with
these cases anyway during SSA destruction so no need to avoid them
earlier.

This fixes backend/ia32_scheduled2.c.

This fixes opt/fehler266.c.