An occurrence range like minOccurs="5" maxOccurs="2" is empty and illegal in
XSD, but the validator accepted it (only the individual values were checked).
occurrenceOrderErrors now compares the two on a particle that carries both: the
comparison is by canonical magnitude (sign and leading zeros stripped, length
then lexicographic), so it holds beyond a machine integer; maxOccurs="unbounded"
is never exceeded and an equal single-point range is allowed.
XSTS: invalid schemas accepted 997 to 977 (-20); valid schemas rejected held at
72; instance buckets unchanged.