Making the menus work in Windows Phone 7, and work better in Android / iOS

[georgestephanis]

A little JS patch that will help the admin menu and the admin bar menus operate properly in mobile devices.

I've probably put some things in the wrong places, and I know nacin/koopersmith sounded like there was another optimization in the JS they'd like to see (koopersmith: we should bind two handlers when a menu is open. one to stop event propagation any time the #adminmenu is clicked, the other to close the menu any time the body is clicked), but I couldn't seem to wrap my head around it, so I'm tapping out to let someone else put the last bit of spit and polish on it.