forward-match in color:text<%>

• (send a-color:text forward-match position cutoff) -> (union natural-number? false?)
     position : natural-number?
     cutoff : natural-number?

  Skip all consecutive whitespaces and comments (using skip-whitespace) immediately following position. If the token at this position is an open, return the position of the matching close, or #f if there is none. For any other token, return the end of that token.

  Must only be called while the tokenizer is started.