Region system

[mothbeanie]

Changes:

This PR adds a map region system. Regions allow the minimap to display only part of a level even if the level has larger bounds (for example, a 5x5 region in a 20x16 level). Regions can also have custom images. If regionid.png is present in /graphics, then the minimap will display that image when the current region is id. The default region is 0, and in region 0 the map will display minimap.png (instead of region0.png) if it is present, in order to maintain forwards compatibility. There are a maximum of 401 regions, from 0 to 400.
It adds three commands to manage them:
setregion(id,x,y,x2,y2) - sets region id from x,y to x2,y2.
changeregion(id) - sets the current region to id. If region id doesn't exist, then it will act as if you aren't in any region at all.
removeregion(id) - removes region id from the array.

Here is a demonstration video:

Regiondemo.mp4

This PR will not break forwards compatibility. Playing a level which uses this system with an older version of the game probably won't even affect their ability to navigate, although they might end up seeing rooms on the minimap that the level creator intended to be outside of the bounds of the displayed map.

Regions are saved to and loaded from a level's save file, as well as what the current region is. The map cursor and icons for trinkets and teleporters will display properly - if the player/a trinket/a teleporter is outside the bounds of the current region, it won't render on the map screen.

This also cleans up a lot of map code, moving more things into MapRenderData. Thanks to Ally and Dav999 for help with this!!!

Legal Stuff:

By submitting this pull request, I confirm that...

• My changes may be used in a future commercial release of VVVVVV
• I will be credited in a CONTRIBUTORS file and the "GitHub Friends"
  section of the credits for all of said releases, but will NOT be compensated
  for these changes

[mothbeanie]

This has been updated to work with the current map code!

[mothbeanie]

This has been updated to work with the current map code. Again.

[InfoTeddy]

I was expecting this to be a quick review. Unfortunately, it wasn't. 😛

I haven't even fully tested everything yet.

[mothbeanie]

Applied changes from the review!

[mothbeanie]

HAHAHAHA OMG OKAY I'LL FIX THAT