Blocks are half-open intervals [a, b), while all other intervals
(chunks, head, ...) are closed intervals [a, b].
Make that distinction explicit by defining `OverlapsClosedInterval()`
methods for blocks and chunks, and using them in place of the more
generic `intervalOverlap()` function.
This change also fixes `db.Querier()` and `db.Delete()`, which could
previously return one extraneous block at the end of the specified
interval.
Signed-off-by: Benoît Knecht <benoit.knecht@fsfe.org>
Benoît Knecht
Simon Pasquier
Mario Trangoni
Fabian Reinartz