Editorial notes (to be continued)

A sequel, starting with Gunther’s observation in the last comment of #2590: * [ ] XQuery: [A.1.2 Constraint: reserved-function-names](https://qt4cg.org/specifications/xquery-40/xquery-40.html#parse-note-reserved-function-names) uses the term "unprefixed" as one of the characteristics of disallowed function names. This may lead one to believe that a `URIQualifiedName` without a prefix might possibly qualify for being restricted. However, this seems unlikely to be intended: the `Q{...}...` syntax is unambiguous and cannot be mistaken for a `KindTest` or similar construct. I thus propose to clarify this in the constraint, by dropping "prefixed"/"unprefixed" from it, or adding a remark about `URIQualifiedName`.