Move eopl language to Racket.

- sllgen.rkt - use begin-for-syntax+define-syntax instead of
  define-syntax-set.
- eopl.scrbl - rewrite *3-columns so that it no longer errors when 3
  doesn't divide the number of reprovided lang forms.
- Removal of mzscheme and mzlib requires.
- Updated docs.
Newlines at EOFs scan.
Some style things.