cached-values-bind: Use svref instead of aref.
Optimize marshalling: pass stack items as two arguments, stack and
offset, not stack+offset.
Simplify the way objects are cached, just strongly cache everything.

Remove the code which was supposed to handle automatic memory
management, it was disabled by default, but could be reinstated in
the future.
Remove guess-stack-item-slot: unused.
deletion_callback: Don't pass smoke object, it's not used.
Clean up: dynamic-object no longer needs to have qt-class metaclass.
Transform NEW into a macro, to get it a chance to be optimized.
qobject: Instead of using a dedicated DELETED slot, set POINTER to :deleted.
Remove PRIMITIVE class, it's only used for enums now.
Remove with-object, with-objects should be used instead.
Put note-deleted calls back, non-qobject objects do notify about their deletion.
Remove more unused functions and variables.
Clean up can-marshal-p.
Inline map-casted-object-pointer.
Don't cache metaobjects, we take ours from slots, and programs
shouldn't need to access it through #_metaObject.
Make CFFI happy with structs.
Reduce expansion size of make-optimized.
Simplify make-optimized further.