More cross-references needed

I noticed this while looking up the optimize-interface section. The last paragraph references :context-declarations in with-compilation-unit. Since with-compilation-unit is defined in the doc, the reference should be a link to that section of the doc. There are quite a few references to with-compilation-unit in the doc; these should all be links.

I suspect there are many other things that should be links but aren't. We should make links for these to make it easier to find things in the manual.