Previously, the value of 'mapgen_limit' was not used to limit the
spawn position.
If a friendly-biome spawn point is not found within a small world,
spawn point falls back to the engine spawn point, which has a larger
chance of success.

To avoid respawn position being possibly very distant from new player
spawn position.

Disabled in mgv6 and singlenode mapgens, by setting, or if
'static_spawnpoint' is set.

Cleanup format of minetest.conf.example.