[m-rev.] for post-commit review: Fix sparse_bitset.divide_by_set.

[Zoltan Somogyi]

On Thu, 13 Oct 2016 17:34:22 +1100, Peter Wang <novalazy at gmail.com> wrote:
> The helper predicate `divide_bits_by_set' compares two bit vectors
> (words) at the same offset, but it was incorrectly passed an absolute
> offset instead of the offset *within* the two words it compares.

The diff is fine.

Zoltan.