Feature: Setting to disallow level crossings with competitors

[mrmbernardi]

Motivation / Problem

See #10311

Players can construct level crossings with other player's roads/rails and cause collisions.

Description

I added a setting which prevents players from constructing level crossings on other player's (or AI's) roads/rails.

It doesn't affect infrastructure constructed by towns or scripts.

Closes #10311 (edit 2TT)

Limitations

Perhaps we should think more about the implications of preventing towns from constructing level crossings.

On one hand, collisions can still occur. On the other, it would be a bit cheesy to block towns from growing with just one rail.
Also, it's harder to grief with the roads towns build.

Checklist for review

Some things are not automated, and forgotten often. This list is a reminder for the reviewers.

• The bug fix is important enough to be backported? (label: 'backport requested')
• This PR touches english.txt or translations? Check the guidelines
• This PR affects the save game format? (label 'savegame upgrade')
• This PR affects the GS/AI API? (label 'needs review: Script API')
  • ai_changelog.hpp, gs_changelog.hpp need updating.
  • The compatibility wrappers (compat_*.nut) need updating.
• This PR affects the NewGRF API? (label 'needs review: NewGRF')
  • newgrf_debug_data.h may need updating.
  • PR must be added to API tracker

[2TallTyler]

Please use the PR template, it's there for a reason to help us review your proposal more easily. 🙂

Also, we typically only use an issue number in the commit when fixing something. A better title for this might be Feature: Setting to disallow level crossings with competitors.

[2TallTyler]

Otherwise looks good to me.

[2TallTyler]

Technology cannot fully prevent griefing, but we can make it less fun.

It's another setting, but it does rhyme with the "allow building road stops" setting so there's precedent for this sort of thing.

Other developers are more than welcome to disagree with me. I won't use this myself, but see no good reason not to add it. 😄

[bjornwarmedal]

I agree with 2TallTyler. It's not a setting I would necessarily use as a social contract generally handles this kind of griefing, but I definitely see where it would be useful.

[mrmbernardi]

I've rebased the branch. One point in favour I'd like to highlight is that this setting is sort of symmetrical to the existing "Allow drive-through road stops on roads owned by competitors" setting.

[2TallTyler]

Sorry, I created a conflict. 😢 I'll re-approve once you rebase.