Mk/Uses/cl.mk: Add USES=cl for Common Lisp ports

[jrm]

Summary

Convert devel/cl-asdf/bsd.cl-asdf.mk to USES=cl. The only real change
is that make files for Common Lisp ports now contain:

USES=cl

rather than

.include "${.CURDIR}/../../devel/cl-asdf/bsd.cl-asdf.mk".

[jrm]

I've done more work on our CL infrastructure, so this revision makes less sense on its own. I will combine it with another review shortly.