Added support for cl-syntax

Added support for cl-syntax.

Although is adds a little bit of complexity to the book's code, it also makes it more portable: loading it doesn't change your readtable, and you can handle read-macros like symbols in a package.

Added an `(eval-when (:compile-toplevel :load-toplevel :execute) ...)` to all read-macro-reading function.

Put the code for the `#f` reader a bit before, before the code stars using the `sharp-backquote` read-macro.

I know it diverges a bit from the book, but makes the `production version` title be more real.