[racket] [ragg] omit escaped tokens from syntax

> What do you think about this? I don't know that much about parsing yet so if there's another way to handle this I'd be interested to hear.

I like the idea.  I've been trying to figure out a nice concise
notation for marking certain patters in ragg as "parse this, but don't
include it in the syntax object."  It shouldn't be too hard to
implement something like this, though I currently don't have time to
work on it immediately.