Add timer() function/event (node timer based) to luacontroller

This adds a timer(<seconds>) function, which causes an event of type
"timer" to be fired after that many seconds has elapsed.

Because it's node timer based, it works properly across server restarts
and block unloading. Thus, simplest example, a blinky plant replacement
with a 10 second period:

if event.type == "program" then
  timer(10)
elseif event.type == "timer" then
  port.a = not port.a
  timer(10)
end

mesecons_luacontroller/init.lua

@@ -219,13 +219,19 @@ local getinterrupt = function(pos)
 	return interrupt
 end
 
-local getdigiline_send = function (pos)
-	local digiline_send = function (channel, msg)
-		if digiline then
-			digiline:receptor_send(pos, digiline.rules.default, channel, msg)
-		end
+local handle_timer = function(pos, elapsed)
+	local err = lc_update(pos, {type="timer"})
+	if err then print(err) end
+	return false
+end
+
+local gettimer = function(pos)
+	local timer = function (time)
+		if type(time) ~= "number" then return end
+		local nodetimer = minetest.get_node_timer(pos)
+		nodetimer:start(time)
 	end
-	return digiline_send
+	return timer
 end
 
 local create_environment = function(pos, mem, event)
@@ -239,7 +245,11 @@ local create_environment = function(pos, mem, event)
 			pin = merge_portstates(vports, rports),
 			port = vports,
 			interrupt = getinterrupt(pos),
-			digiline_send = getdigiline_send(pos),
+			timer = gettimer(pos),
+			digiline_msgs = {},
+			digiline_send = function(channel, msg)
+				table.insert(lc_digiline_msgs, {["channel"]=channel, ["msg"]=msg})
+			end,
 			mem = mem,
 			tostring = tostring,
 			tonumber = tonumber,
@@ -527,6 +537,7 @@ minetest.register_node(nodename, {
 		if err then print(err) end
 		reset_meta(pos, fields.code, err)
 	end,
+	on_timer = handle_timer,
 	sounds = default.node_sound_stone_defaults(),
 	mesecons = mesecons,
 	digiline = digiline,