1.0.29.45: another CTOR optimization

1.0.29.45: another CTOR optimization

* If we're forced to use the fallback generator, but the initargs can be
  verified early on and there are no extra methods on MAKE-INSTANCE
  we don't have to go through full MAKE-INSTANCE: instead use
  FAST-MAKE-INSTANCE. 1 less GF call and no initarg checking at runtime
  yields a ~2-4 fold performance improvement.