Ports ping verb from /tg/ (#7837)

* Ports ping verb from /tg/

* Adds non-versioned files

* Removes old flag

code/controllers/subsystems/ping.dm

@@ -0,0 +1,30 @@
+#define PING_BUFFER_TIME 25
+
+SUBSYSTEM_DEF(ping)
+	name = "Ping"
+	wait = 6
+	flags = SS_NO_INIT|SS_POST_FIRE_TIMING
+	priority = FIRE_PRIORITY_PING
+	init_order = INIT_ORDER_PING
+	runlevels = RUNLEVEL_LOBBY|RUNLEVEL_SETUP|RUNLEVEL_GAME|RUNLEVEL_POSTGAME
+	var/list/currentrun
+
+/datum/controller/subsystem/ping/fire(resumed = FALSE)
+	if (!resumed)
+		src.currentrun = GLOB.clients.Copy()
+
+	var/list/currentrun = src.currentrun
+	while (length(currentrun))
+		var/client/C = currentrun[currentrun.len]
+		currentrun.len--
+		if (!C || world.time - C.connection_time < PING_BUFFER_TIME)
+			if (MC_TICK_CHECK)
+				return
+			continue
+		winset(C, null, "command=.update_ping+[world.time+world.tick_lag*world.tick_usage/100]")
+		if (MC_TICK_CHECK) //one day, when ss13 has 1000 people per server, you guys are gonna be glad I added this tick check
+			return
+
+	currentrun = null
+
+#undef PING_BUFFER_TIME