Movement smoothness tweaks (#1736)

This PR ports /tg/'s movement verbs, which allow for smoother movement that's less dependent on server tick rate.

Also ports /tg/'s Stat() limiter, which reduces how often Stat() updates to reduce pointless server load.

code/modules/client/client procs.dm

@@ -610,3 +610,15 @@
 	server_greeting.find_outdated_info(src, 1)
 
 	server_greeting.display_to_client(src)
+
+// Byond seemingly calls stat, each tick.
+// Calling things each tick can get expensive real quick.
+// So we slow this down a little.
+// See: http://www.byond.com/docs/ref/info.html#/client/proc/Stat
+/client/Stat()
+	. = ..()
+	if (holder)
+		sleep(1)
+	else
+		sleep(5)
+		stoplag()