[plt-scheme] Discrepancies in the documentation for PLT's Intermediate Student Language w/ Lambda

I've noticed a couple of discrepancies between the documentation for
Intermediate Student Language w/ Lambda and the actual results from
the REPL.

In particular  the following are listed as primitive operations, but
DrScheme's REPL claims they are undefined identifiers:
string->int
replicate
string-ith

I also think string-ith's contract is wrong.

There might be other that I haven't stumbled upon yet.

Also, the grammar for the language lists (quoteid) as a type of expr,
I believe this should be (quote id) with a space.

-- 
Dan King
College of Computer and Information Science
Northeastern University
danking at ccs.neu.edu