Scheme strings not highlighted inside define #7

GitHub uses this TextMate bundle for Scheme highlighting, and in the following code, the string is not highlighted:

(define (x) "test")

In general, any expressions directly in the body of (define (...) ...) should get highlighted the same as in the body of (begin ...):

(begin
  ; Comment
  "string"
  'symbol
  ' symbol
  #t
  #f
  1234
  -1234.0e1234
  0x09AF
  0b010101
  #\space
  #\x0A
  #\a
  '())

(define (x)
  ; Comment
  "string"
  'symbol
  ' symbol
  #t
  #f
  1234
  -1234.0e1234
  0x09AF
  0b010101
  #\space
  #\x0A
  #\a
  '())

On the TextMate manual page for language grammars, the following snippet is suggested for parentheses nesting:

{  begin = '\('; end = '\)'; patterns = (
      { include = "$self"; }
   );
}

This Scheme syntax grammar does not currently include $self for the body of (define (...) ...), but it instead includes an incomplete list of expression types: #comment, #sexp, and #illegal (#string is missing). By changing this to simply $self, these kinds of problems can be avoided.