Add support for (contract-out (rename ....))

[bennn]

SCV should be able to parse renames in a contract-out

Example:

#lang racket/base
(define (f x) (+ x x x))

(require racket/contract)
(provide (contract-out
  (rename f myf (-> integer? integer?))))

raco scv errors with f:provide: unexpected term at: myf