Class ExtendedIntervalIterator


class ExtendedIntervalIterator extends IntervalIterator
Wraps an IntervalIterator and extends the bounds of its intervals

Useful for specifying gaps in an ordered iterator; if you want to match `a b [2 spaces] c`, you can search for phrase(a, extended(b, 0, 2), c)

An interval with prefix bounds extended by n will skip over matches that appear in positions lower than n