Minor errors in documentation

[rebcabin]

in section 2 are a couple of nit-picky mistakes, I think. My edits below in square brackets.

Local binding forms. The local form accommodates multiple definitions that [ARE] visible only among the definitions and the body expr. The letrec, let, and let* forms bind each id to the value of the corresponding rhs-expr (where the rhs-exprs are evaluated in order). In the case of letrec, each id is visible to every rhs-expr as well as in the body expr. In the case of let, each id is visible only in the body expr. In the case of letrec, [I THINK THIS SHOULD BE LET-STAR] each id is visible only to later rhs-exprs as well as in the body expr.