uma_zcreate: additional arg for uminit/fini

[Andriy Gapon]

What do you think about adding an argument to uma_zcreate that would be passed
on to uminit/fini as an additional parameter?
Perhaps (probably?) to dtor/ctor.

The idea is to provide additional context to uminit/fini.
One immediate use is more efficient compatibility code for OpenSolaris kmem_cache:
http://docs.sun.com/app/docs/doc/816-5180/kmem-cache-create-9f?a=view

-- 
Andriy Gapon