Map generation limit: Make per-world

[paramat]

The setting limits map generation but affects nothing else.
Add 'mapgen_limit' to global mapgen parameters.
Move 'blockpos_over_mapgen_limit()' to the only place it is called
from: map.cpp.
Allow teleportation to any part of the world even if over the set
mapgen limit.
Simplify the reading of this limit in mgvalleys.
Remove the 'map_generation_limit' setting.
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Addresses #1608
This is a new version of #4338 i have copied some of the code by SmallJoker.

[rubenwardy]

I think that this would be better implemented by making per-world settings, personally - as mapgen limit seems to be a setting currently, rather than a mapgen config

[paramat]

Mapgen limit is a setting but should not have been, it is a fundamental mapgen parameter like water_level that causes problems when not per-world and when people forget to change the setting for each world they enter.
For many settings i would agree with you but this one belongs grouped with the other basic mapgen paramters.

[paramat]

In testing this works.

I am not happy with how the mapgen limit setting is grabbed by passing settings_mgr.mapgen_params from the place of the call, how can we grab the value directly in mapblock.h?
Maybe the blockpos_over_mapgen_limit() function should be moved to map.cpp to avoid having to pass stuff? I'll try it.

[paramat]

Updated, need to test.

[paramat]

Tested, adds the new parameter to existing worlds on update, whether the parameter is set non-default or not.
I'll add docs once this gets some approval.

[SmallJoker]

LGTM

[nerzhul]

okay for me

[paramat]

Added docs and re-added new setting to defaultsettings.cpp (oops).

[paramat]

Retested and fine.
Will make a forum post about updating the setting.

[paramat]

ec0c4d3