Our code gets references to 8 or 16 byte structs by casting pointers into
LMDB data.
1. In a database with no DUPs and 8 byte (u64) keys, can we expect the
corresponding value to have alignment 8?
2. In a database with DUPs and 8 byte (u64) keys, if a DUP value (stored as
a key internally) is 16 bytes, does it mean that its alignment is 16? Does
the 8 byte key size impact the alignment of its DUPs as it does in 1.?