Add option to disable lavacooling (#1726)

functions.lua

@@ -131,6 +131,7 @@ default.cool_lava = function(pos, node)
 		{pos = pos, max_hear_distance = 16, gain = 0.25})
 end
 
+if minetest.setting_getbool("enable_lavacooling") ~= false then
 	minetest.register_abm({
 		label = "Lava cooling",
 		nodenames = {"default:lava_source", "default:lava_flowing"},
@@ -142,7 +143,7 @@ minetest.register_abm({
 			default.cool_lava(...)
 		end,
 	})
-
+end
 
 --
 -- optimized helper to put all items in an inventory into a drops list