Stop clang from crashing
Implement vector and multivector iterators with boost::iterator_facade

This should make the iterators to really comply with the
std::random_access_iterator_tag. Also should solve issue #90.
Merge pull request #91 from ddemidov/iterator_facade

Implement vector and multivector iterators with boost::iterator_facade
Spell out size_t type name in stride loop generation

size_t and ulong are different types on MacOSX, so no overload for
max(size_t, ulong) could be found.

See discussion in #91.
Do not use min in grid stride loop setup.

This avoids problems with min on MacOsX (see #92)