The option has no effect.
This closes#3566
The block cache was added originally to work around perceived slow hash table lookups in the database.
By having an in-memory dictionary, lookups would be much faster.
It has no effect on disk wear, as the lookups are read-only.
The impact of such a cache was measured to be minimal with recent versions of SQLite.
Kenneth Skovhede
f5cabd4c7f