nested-loop documented but not exported

[Symbolics]

There's a note in all.lisp:

;; Note: array-operations/utilities not exported for external use.

[bendudson]

Good point. I guess no-one else had ever tried to use it :) Is this useful enough to export, or should the documentation for nested-loop just be moved to the end of the docs and marked as an internal utility?

[Symbolics]

I think it's useful enough to export

[Symbolics]

In aops, Tamas is using the package-inferred-system from ASDF and I'm not familiar enough with it to want to try to change it just yet. The symbol is exported, but you have to explicitly use or import from the array-operations/utilities package. I'll document that fact and then close this.