Adjust WAL checkpoint interval.

Currently the auto-checkpoint interval is 1 page, which makes poor
use of WAL and causes additional unnecessary synchronous writes to
the main database file.

Set the checkpoint interval to 100 pages to make better use of WAL
while still avoiding long checkpoint pauses.

Change-Id: Id54ac02406613bb9379d2116d51947de1d7a489c
1 file changed