Fix for getPointer on touchDevices + Fix for absolute postioned scrolled elements

Fix touch events if canvas is inside a scrolled container (see issue #123).

Fix bug if mouse moves over absolute scrolled element while object scaling (see issue #385). Also if mouse is moved over documentElement (fabric.document) while scaling object is fixed (same issue like #385).

Tested with Safari 5.1.7, 6.1, Firefox 18, 3.6.28, Chrome 24/25beta, Opera 12.12 and iPhone iOS 6.1, iPad iOS 6.1 in non-scrolled and scrolled containers.