Add whitespace folding for some atomic data types that it's missing on.

XSD validation fails when some atomic types contain surrounding whitespace
even though XML Schema Part 2: Datatypes Second Edition, section 4.3.6
says they should be collapsed. Fix this.

(I am not sure whether the test is correct.)

Issue: #278
4 jobs for atomic-whitespace-folding in 7 minutes and 7 seconds (queued for 4 seconds)