Prevent scroll bars appearing in respawn UI at low resolutions

(as per) http://citystate.vanillaforums.com/discussion/comment/183496/#Comment_183496

When the screen size is reduced to the smallest it will allow, the re-spawn UI is generating scroll bars, perhaps because the div that is a child of body is set to a fixed with (so that margin 50% centring works).  As this div is centred within the body regardless of how big the body is, then having the body hide any scroll bars if there is a bit of clipping at the edge makes complete sense (to me at least).