Remove obsolete random basement/house combo creation

[ralreegorganon]

Summary

SUMMARY: None

Purpose of change

This retires all of the code that would randomly combine a random house with a random basement in order to sometimes add houses with basements to cities.

This code was made obsolete as part of the 0.E release with the move to having all houses defined as city_building entries with specific house, basement and roof entries.

Describe the solution

Pull the thread and nuke everything that was no longer needed, including:

• entries in the regional settings for the basements
• entries in the regional settings for the chance for a house to have one of these basements
• the code that attempted to add stairs to a house that was created by smushing together a basement and house
• the ALIGN_STAIRS system setting which was only used by the aforementioned stair creation code
• the code that attempted to determine if a location had a basement based on it having one of the defined basement entries, only used by the same aforementioned stair creation code

Describe alternatives you've considered

None. This needs to go lest it confuse anyone doing new content creation.

Testing

Made a new world, ran around, made sure no errors triggered. Did the same with an old world.

Our previous PRs that actually retired the houses and basements bore the brunt of the issues for this--at this point, the only part of this code that could've been invoked would be the code that would place stairs, but it would only invoke for the local mapgen of a house OMT that had a basement OMT underneath it, and we've migrated all of the house OMTs to house_w_1 which has stairs down, and our basement has stairs up.

Folks with existing worlds with previously local mapgen'd houses may have weird stairs, but this has no bearing on that.

[ZhilkinSerg]

src/mapgen_functions.cpp:54:9: error: macro is not used

  [-Werror,-Wunused-macros]

#define dbg(x) DebugLog((x),D_MAP_GEN) << FILE << ":" << LINE << ": "

    ^

[kevingranade]

This pull request has been mentioned on Cataclysm: Dark Days Ahead. There might be relevant details there:

https://discourse.cataclysmdda.org/t/align-up-stairs-and-downstairs/25362/2