Angled Stairs by TumeniNodes

Adds angled stairs to the Minetest Game.

Adds a new and unique style of stairs to Minetest. Useful for angled elevations, as well as to build spiral-like-ish staircases! They can also be manipulated with the screwdriver, so they add some other options for building.

My thanks to everyone who took the time to help and advise (as well as time spent working on portions of this mod) Napiophelios, for all the help adding support for default textures. sofar, for putting time into helping with models. pithy, for putting time into helping with models (models provided by pithy). Nathan S, for offering help with Lua. azekill_DIABLO, for adding some advice regarding performance.

Also, if anyone wishes to add crafting recipes for them, that would be awesome. I don't use them, I just build stuff : )