BitvSet::is_disjoint is reversed

[zwarich]

The implementation of BitvSet::is_disjoint is this:

    #[inline]
    fn is_disjoint(&self, other: &BitvSet) -> bool {
        self.intersection(other).count() > 0
    }

It also shouldn't use count; it can just check whether the intersection iterator is empty directly.

[Gankra]

On it