1.0.40.2: ctor machinery bugfixes

1.0.40.2: ctor machinery bugfixes

One bug was a simple harmless thinko, limiting the cache for validity
checking of reinitialize-instance initargs to only one list of keys.

The other is actually a correctness problem: addition or removal of
methods on MAKE-INSTANCE and ALLOCATE-INSTANCE would invalidate the
wrong set of initarg validity caches and reset the wrong ctors.  I
think at the moment this bug is tricky to trigger, because those
methods have no effect on reinitialize-instance initarg checking, and
fallback ctors on non-standard metaclasses are very conservative in
their assumptions.