Using an edata_t both for hugepages and the allocations within those hugepages was convenient at first, but has outlived its usefulness. Representing hugepages explicitly, with their own data structure, will make future development easier.
This isn't a tree any more, and it mildly irritates me any time I see it.
This frees us up from the unfortunate extent/extent2 naming collision.
This name is slightly pithier; a full-on rename will come shortly.
