Proposed text changes to Touch Events v1

I have action items (72 and 73) to propose text to address Issue-21
(Description of touchcancel event is missing some details) and Issue-22
(Does an element have to also register for touchstart event in order to
receive touchend/touchmove events). Here are the proposed text changes.

In 5.1 Attributes, for changedTouches, add touchcancel event to the last
sentence on the behavior for touchend event. Thus,
For the touchend and touchcancel events this must be a list of the touch
points that have just been removed from the surface.

In 5.5 The touchend event, replace "Element that received the touchstart
event" in the second paragraph with "Element on which the touch point
started", and some cosmetic changes. Thus, 
The target of this event must be the Element on which the touch point
started when it was first placed on the touch surface, even if the touch
point has since moved outside the interactive area of the target element.

In 5.6 The touchmove event, same change as in 5.5.
The target of this event must be the Element on which the touch point
started when it was first placed on the touch surface, even if the touch
point has since moved outside the interactive area of the target element.

In 5.7 The touchcancel event, add the following paragraphs:
The target of this event must be the Element on which the touch point
started when it was first placed on the touch surface, even if the touch
point has since moved outside the interactive area of the target element.
The touch point or points that were removed must be included in the
changedTouches attribute of the TouchEvent, and must not be included in the
touches and targetTouches attributes.

Comments are welcome. I'd be happy to commit the changes if the group agrees
with the changes and the editors are ok with me doing it.

Regards, Cathy.