The timestamp offset of a block was being converted from i16 to u64, so
negative values would overflow and cause timestamps that fall before
the cluster's timestamp from being close to the minimum representable
i64.
The math is also now done using saturating operations to prevent any
other similar issues from occurring.
These aren't particularly small objects, but we were still copying them
around all over the place. When TrackEntry contains data buffers, they
won't need to be copied as well.
