This fixes an extent searching regression on 32-bit systems, caused by the initial bitmap_ffu() implementation in c8021d01f6efe14dc1bd200021a815638063cb5f (Implement bitmap_ffu(), which finds the first unset bit.), as first used in 5d33233a5e6601902df7cddd8cc8aa0b135c77b2 (Use a bitmap in extents_t to speed up search.).