yui/yui3 — pull request #75 by okuryu (2012-02-01 12:05:18+00:00)
Title: Add detects Windows Phone devices.

Recently, It's feels Windows Phone 7 is one of modern mobile OS. These devices can be detected by finding the ```IEMobile``` token.

The following example user agent:

```
Mozilla/5.0 (compatible; MSIE 9.0; Windows Phone OS 7.5; Trident/5.0; IEMobile/9.0; FujitsuToshibaMobileCommun; IS12T; KDDI)
```

How it works:

```javascript
if (Y.UA.ie) {
if (Y.UA.mobile) {
// I am IE Mobile (Windows Phone).
} else {
// I am IE (PC).
}
}
```

See also about detection:
http://windowsteamblog.com/windows_phone/b/wpdev/archive/2011/08/29/introducing-the-ie9-on-windows-phone-mango-user-agent-string.aspx

Please review.