Adjusted sync/single arg passing + minor touches on the spec.

* Generic and blank-intent sync/single passing - by ref. It used to specify readFE/readFF(), which I changed according to #420.

* Since the section opens with "normal reads and writes", I used "normal" consistently throughout several parts of the section that talks about reads and writes.

* Call 'sync', 'single' "type qualifiers" consistently.

I did not see any other places in the spec that needed an update for #420, although I did not look too hard. The subsections on "Formal Arguments" and "Argument Intents" mention sync/singles only in the abstract-intent tables for blank and const, and those are correct IMO.