BugFix: test for parity on unordered compares

added cbc verifier

- patching node inputs fool the register verifier, so fxch, fpop and fpush are now nodes
  without in- and output. They are keeped and hold in the schedule.
- handle all possible constants in sim_Copy()

NEVER return st registers for a floating point node, or the x87 simulator fails

emit block labels for switchjmp targets

 - use of wrong (uninitialized) variable
 - modes was fixed to mode_Iu, but must be the same mode as the other tarval