As discussed on the racket users list (subj: ~literal vs ~datum) at https://groups.google.com/d/msg/racket-users/KWANfGc7qcI/G_MClWJpBAAJ
New example based on code from Jens Axel Soegaard.
Caveat: I've run this in DrRacket with (require (for-syntax syntax/parse)) to verify the three distinct outputs, but am submitting this PR in-browser, so I haven't run the doc build on it myself.
* Fixed typo in the docs for serialization (serializable-struct/version → serializable-struct/versions)
* Fixed typo in scribble documentation (head pattern → a-pattern)
* Made the order of the argument descriptions match the order of the arguments in the documentation for import and export
