Recognition for IE11, Opera 15+ and Maxthon, made Win 8.1 for version 1.X

If you reject pull request https://github.com/piwik/piwik/pull/161 for the master branch (i.e. Piwik 2.0+), you may still want to consider these updates for Piwik 1.x (1.13 going forward).

Piwik 1.12 currently doesn't recognize IE11, Windows 8.1 and Maxthon. Opera versions 15+ are wrongly identified as Google Chrome.