For the MLD algorithm we can partition the NodeID range into boundary
and non-boundary nodes. Since there are only we boundary nodes we can
use the ArrayStorage for those yielding much faster query times.
Default-constructed objects of (boost::heap) handle_type are singular,
including the wrapped handle_type::iterator.
Apparently, MSVC iterator debug facilities strictly require that
one singular instance is compared to another singular instance.
It is not possible to get check-comparabe iterators of non-singular
and singular instances as owning container will always mismatch.
