[CM] R7RS support

[bil at ccrma.Stanford.EDU]

The with-exception definition in r7rs.scm probably should be

(define (with-exception-handler handler thunk)
   (catch #t thunk (lambda args (apply handler args))))

The define-library code dates from the days (years ago)
when s7's define-macro returned the symbol rather than
the value.  Also, I apparently missed the built-in library
for r5rs names.  For the latter add

(apply define (symbol (object->string '(scheme r5rs))) (inlet) ())

For the former

295c296
< 			 (cons 'export (symbol->value
---
> 			 (cons 'export ;(symbol->value
297c298
< 					  `(set! *export* (append ',names *export*))))))
---
> 					  `(set! *export* (append ',names *export*)))));)

That is, symbol->value is probably not needed anymore.