Stop relying on `syntax-original?`

[jackfirth]

It's brittle and doesn't quite mean what I intend. Really what I'm looking for is a way to check that a syntax object came directly from the output of source-read-syntax. I think I can solve that by adding an interned scope to the output of source-read-syntax, or something like that.

Fixing this would make it possible for refactoring rules to operate on the whole (module ...) form produced by the reader.