Add support for (MS) pointer events for tap

IE10/11 doesn't implement Apple's touch events. Instead, they developed [pointer events](http://www.w3.org/TR/pointerevents/). This adds support for pointer events as described in the spec and as implemented in IE10/11 (prefixed). Tested in IE10.

Are there automated tests for the event definitions somewhere? I couldn't find any.

I also was a bit unsure about the handling of pointercancel. In the touchcancel variant below there are no checks regarding the touch identifier, so I didn't add any for pointercancel. I guess partial touch canceling isn't actually possible.