Add flambe_disable_hide_mobile_browser.

This disables the scrollTo() hack that hides the location bar in some
mobile browsers. Since it seems to only work in iOS 6 and Android 2.x,
I'm thinking about removing it altogether, but for now it's behind a
compiler flag.

http://www.html5gamedevs.com/topic/3848-windowscrollto-hack-to-hide-mobile-address-bar-still-relevant/