Added worldedge mod (with little tweak)

- Added worldedge mod by @DonBatman
 - Solves #50

mods/worldedge/README.md

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+worldedge
+=========
+
+A Minetest Mod that teleports you to the other side of the map when you reach its edge.
+This gives the illusion that that world is round and you can walk all the way around.
+
+You can change the worlds edge by changing the first variable in init.lua
+	local edge = 30000
+
+License of code: WTFPL
+
+Written by Amaz
+Modified by Don

mods/worldedge/init.lua

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+--------------
+-- TODO: Check for terrain height
+
+-- Defines the edge of a world
+local edge = 30000
+-- Radius which should be checked for a good teleportation place
+local radius = 2
+--------------
+
+local count = 0
+local waiting_list = {}
+--[[ Explanation of waiting_list table
+	Index = Player name
+	Value = {
+		player = Player to teleport
+		pos = Destination
+		obj = Attacked entity
+		notified = When the player must wait longer...
+	}
+]]
+
+minetest.register_globalstep(function(dtime)
+	count = count + dtime
+	if count < 3 then
+		return
+	end
+	count = 0
+
+	for k, v in pairs(waiting_list) do
+		if v.player and v.player:is_player() then
+			local pos = get_surface_pos(v.pos)
+			if pos then
+				v.obj:setpos(pos)
+				minetest.after(0.2, function(p, o)
+					p:set_detach()
+					o:remove()
+				end, v.player, v.obj)
+				waiting_list[k] = nil
+			elseif not v.notified then
+				v.notified = true
+				minetest.chat_send_player(k, "Sorry, we have not found a free place yet. Please be patient.")
+			end
+		else
+			v.obj:remove()
+			waiting_list[k] = nil
+		end
+	end
+
+	local newedge = edge - 5
+	-- Check if the players are near the edge and teleport them
+	local players = minetest.get_connected_players()
+	for i, player in ipairs(players) do
+		local name = player:get_player_name()
+		if not waiting_list[name] then
+			local pos = vector.round(player:getpos())
+			local newpos = nil
+			if pos.x >= edge then
+				newpos = {x = -newedge, y = 10, z = pos.z}
+			elseif pos.x <= -edge then
+				newpos = {x = newedge, y = 10, z = pos.z}
+			end
+
+			if pos.z >= edge then
+				newpos = {x = pos.x, y = 10, z = -newedge}
+				newpos.y = get_surface_pos(newpos).y
+			elseif pos.z <= -edge then
+				newpos = {x = pos.x, y = 10, z = newedge}
+				newpos.y = get_surface_pos(newpos).y
+			end
+
+			-- Teleport the player
+			if newpos then
+				minetest.chat_send_player(name, "Please wait a few seconds. We will teleport you soon.")
+				local obj = minetest.add_entity(newpos, "worldedge:lock")
+				player:set_attach(obj, "", {x=0, y=0, z=0}, {x=0, y=0, z=0})
+				waiting_list[name] = {
+					player = player,
+					pos = newpos,
+					obj = obj
+				}
+				obj:setpos(newpos)
+			end
+		end
+	end
+end)
+
+function get_surface_pos(pos)
+	local minp = {
+		x = pos.x - radius - 1,
+		y = -10,
+		z = pos.z - radius - 1
+	}
+	local maxp = {
+		x = pos.x + radius - 1,
+		y = 50,
+		z = pos.z + radius - 1
+	}
+
+	local c_air = minetest.get_content_id("air")
+	local c_ignore = minetest.get_content_id("ignore")
+
+	local vm = minetest.get_voxel_manip()
+	local emin, emax = vm:read_from_map(minp, maxp)
+	local area = VoxelArea:new{MinEdge = emin, MaxEdge = emax}
+	local data = vm:get_data()
+
+	local seen_air = false
+	local deepest_place = vector.new(pos)
+	deepest_place.y = 50
+
+	for x = minp.x, maxp.x do
+	for z = minp.z, maxp.z do
+		local solid = 0
+		for y = deepest_place.y, -10, -1 do
+			local node = data[area:index(x, y, z)]
+			if y < deepest_place.y and node == c_air then
+				deepest_place = vector.new(x, y, z)
+				seen_air = true
+			end
+			if solid > 5 then
+				-- Do not find caves!
+				break
+			end
+			if node ~= c_air and node ~= c_ignore then
+				solid = solid + 1
+			end
+		end
+	end
+	end
+
+	if seen_air then
+		return deepest_place
+	else
+		return false
+	end
+end
+
+minetest.register_entity("worldedge:lock", {
+	initial_properties = {
+		is_visible = false
+	},
+	on_activate = function(staticdata, dtime_s)
+		--self.object:set_armor_groups({immortal = 1})
+	end
+})