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
The symbol is used as the "who" field in the error message.
Also fix lazy-require of runtime-report.rkt in residual.rkt; don't
load until syntax-parse actually needs to produce an error report.
(Previously was loaded to create handler whenever syntax-parse code ran.)
