Imposes an ascending ordering based on the end points of basic intervals.
For mapped basic intervals, the register numbers are also compared.
Note that this ordering would be inconsistent with equals if both objects
of type BasicInterval and MappedBasicInterval were contained
in the set. A comparison of a MappedBasicInterval with a BasicInterval may
consider both to be the same because their begin and end are the same but
the equals methods would not consider the objects as equal.