Tentative IE11 user-agent detection

For reference:

http://msdn.microsoft.com/fr-fr/library/ie/bg182625%28v=vs.85%29.aspx#uaString 

The changes should bring the additional benefit of simplifying a wee bit the detection of less ancient versions of IE, as from IE 8 on, all bear "Trident" in the user-agent string .

***WARNING**

This is still untested code!