Editorial: use more terms from the Infra Standard

In particular:

* ASCII whitespace
* ASCII digit
* ASCII hex digit (and lower/upper)
* ASCII alpha (and lower/upper)
* ASCII alphanumeric
* strip newlines
* strip leading and trailing ASCII whitespace
* strip and collapse ASCII whitespace
* collect a sequence of code points
* skip ASCII whitespace
* strictly split a string (not actually used in HTML)
* split a string on ASCII whitespace
* split a string on commas