Postgres 9.5 deprecated checkpoint_segments, now uses min_wal_size, max_wal_size instead

[xpe]

I just ran pgtune. It suggested an adjustment to checkpoint_segments. However, according to https://www.postgresql.org/docs/9.6/static/release-9-5.html, checkpoint_segments is no longer present:

Replace configuration parameter checkpoint_segments with min_wal_size and max_wal_size (Heikki Linnakangas)

If you previously adjusted checkpoint_segments, the following formula will give you an approximately equivalent setting:

max_wal_size = (3 * checkpoint_segments) * 16MB

Note that the default setting for max_wal_size is much higher than the default checkpoint_segments used to be, so adjusting it might no longer be necessary.

[andreif]

It will be fixed via #18.