Can I implement reader macros? let’s see!

We don’t need (at least, in the Clojure reader) to rewrite forms like 'FOO, because that’s handled by the parser. But we do need to rewrite things which don’t evaluate their arguments, like SETQ, because (unless LABEL does it, which I’m not yet sure of) we’re not yet able to implement things which don’t evaluate arguments.

TODO: at this stage, the following should probably also be read macros: DEFINE