More:

mdb_cursor_put() now tracks data items instead of keys in md_entries, broken by 13d6d59c512065db3741c20c65b4d9928b986968.

mdb_cursor_del(, MDB_NODUPDATA) is off-by-one for sub-DBs: It subtracts subDB.md_entries, then mdb_cursor_del0() subtracts 1.

Fixing.