Brooms, Stick-horses, and Flying Wizards!

A port of https://github.com/d3athrow/vgstation13/pull/4377

![image](http://i.gyazo.com/dd415093be904dc9e5d40570598eddb9.gif)

Allows brooms to be wielded with 2-hands. Doing so places the broom
between your legs so you look like you are riding it.

You can also put a horsehead mask onto the broom to create a stick-horse
to ride. This can also be wielded, but will ALWAYS appear between your
legs.

And for the more magically inclined, wielding a broom or stick-horse (2
hands!) will cause you to ride it like a witch, giving you the ability
to bypass hazards such as tables and banana peels.

code/game/objects/structures/tables_racks.dm

@@ -334,6 +334,10 @@
 	if(air_group || (height==0)) return 1
 	if(istype(mover,/obj/item/projectile))
 		return (check_cover(mover,target))
+	if(ismob(mover))
+		var/mob/M = mover
+		if(M.flying)
+			return 1
 	if(istype(mover) && mover.checkpass(PASSTABLE))
 		return 1
 	if(locate(/obj/structure/table) in get_turf(mover))