.scrollRect for html5. Second try.

Since there were too many conflicts with latest version of NME and my .scrollRect pullrequest, i've forked NME again and implemented .scrollRect again.

This time i've tested a lot, and now it looks pretty stable, except on my system in chrome changing scrollRect.x and scrollRect.y looks delayed (everything ok in firefox). Thus more testing by other people still required.

Here is my test platform: http://stablex.ru/ui/demo/masking2/
There is one object with .scrollRect in test - white square. Objects are large, so it's better to play with it on fullhd display.

Here is another example with ~350 display objects on stage: http://stablex.ru/ui/demo/demo_html5/
There are scrollRect`ed objects inside other scrollRect`ed objects, and everything looks fine.