Bad error message for define-like things

This gives a bad syntax error:

```
#lang class/0
(define-class a%
  (define/asdf (m) 1))
```

which is

```
define-class: There were multiple syntax errors. The first error follows:
expected the identifier `isl+:check-range' in: define/asdf
```

Obviously the `isl+:check-range` is a nasty implementation artifact. 
