Horse roam radius like the happy ghast

I believe that since the Mounts of Mayhem are coming and Mojang is working on the mounts, it would be wise to implement the same mechanics for horses that the Happy Ghast has, which roams in place depending on where one has 'parked' it.

The horse is terrible to leave on its own, because it vanishes, never to be seen again, if one doesn't carry a lead and a fence everywhere to hitch the horse. Some mods already do that in Java, as well as letting the player ride on water (which is going to be implemented on the next update)