Syntax-Case Macros for PEG Parser

[Michael Lucy]

I'm still working on this.  I haven't dropped off the face of the
earth; it's just taking a bit.  The way I wrote the original
define-macro macros, they called some functions (passing in symbol
names) to generate blocks of code.  This technique essentially depends
on variable capture, so I can't really do it with syntax-case (at
least not without twisting things into an obscene shape).

Anyway, the transformations aren't terribly difficult, they just
involve a lot of hand-rewriting to turn all the function calls into
actual macro expansions.  I think I'll be done reasonably soon.