Adding new slot-options to defclass?

[Shannon V Spires <svspire@somnet.sandia.gov>]

I need to add a new slot option (like :accessor, :initarg, etc.)
to certain slots in a defclass. The idea is that I would
do some "special" processing as the class is being defined
whenever a new slot option, like :foo, appeared in a slot
description.

What's the best way to do this? Ideally, one could write a method
on make-instance, allocate-instance, initialize-instance, etc.,
but I cannot find any evidence that MCL calls these functions
when it's creating an instance of a metaclass (that is, doing
a defclass). Is there any other way, or must I just rewrite
the defclass macro?

Thanks,
Shannon Spires
svspire@sandia.gov