Fix diagonal fire-spread

In Minecraft fire spread logic, “adjacent” does not mean “diagonal”.

mods/ITEMS/mcl_fire/init.lua

@@ -27,8 +27,30 @@ local spawn_smoke = function(pos)
 	}, "high")
 end
 
+local adjacents = {
+	{ x =-1, y = 0, z = 0 },
+	{ x = 1, y = 0, z = 0 },
+	{ x = 0, y = 1, z = 0 },
+	{ x = 0, y =-1, z = 0 },
+	{ x = 0, y = 0, z =-1 },
+	{ x = 0, y = 0, z = 1 },
+}
+
+local function shuffle_adjacents()
+	for i = #adjacents, 1, -1 do
+		local r = math.random(i)
+		adjacents[i], adjacents[r] = adjacents[r], adjacents[i]
+	end
+end
+
 local function has_flammable(pos)
-	return minetest.find_node_near(pos, 1, {"group:flammable"})
+	for k,v in pairs(adjacents) do
+		local p=vector.add(pos,v)
+		local n=minetest.get_node_or_nil(p)
+		if n and minetest.get_item_group(n.name, "flammable") > 0 then
+			return p
+		end
+	end
 end
 
 --
@@ -387,6 +409,7 @@ else -- Fire enabled
 			local p = get_ignitable(pos)
 			if p then
 				spawn_fire(p)
+				shuffle_adjacents()
 			end
 		end
 	})