Add $.browser.mobile to check for mobile browsers

[dalangalma]

It's often useful to present reduced functionality (or just turn off a lot of JavaScript spiffiness) for mobile browsers. A $.browser.mobile flag would help out a lot.

[flesler]

Hi, we don't do any specialized code in the core, according to whether the browser is on a mobile or not. This means the core doesn't need this sniffing, you can add it externally.

Something like:

  jQuery.browser.mobile = /mobile/i.test(navigator.userAgent);