[racket] syntax-parse and literals

I guess to me, the term "literal identifier" is an oxymoron.  It's
either a literal (5, #f, in this case :) or an identifier (foo, car,
+).  Unless "identifier" means nothing more or less than "symbol".

When I write (:) in syntax-case, I'm saying ": is not a binding form;
I want to see literally a :, and I don't want to bind the : in the
pattern to whatever you find in that position".  I'm trying to
reproduce that effect here.

Shriram