fixes #17810 touch/pointer events feature detection.
- clarifies has("touch")
- adds has("touch-events"), has("pointer-events") and has("MSPointer")
- updates code in dojo/dijit/dojox to use the new has (only when it does not impact the current logic).
Merge pull request #95 from seb-pereira/t17810

fixes #17810 touch/pointer events feature detection.