Glitched artifacts with blurred items inside a scrollable container about haze

[chrisbanes]

So there's 2 issues here by the look of it:

• The first (the white flashing), where our clipOutRect isn't not working when an image is used. This is likely some deep drawing bug (maybe this is just doing too much).

• The second (the overlapping areas), which looks like an issue only with Lazy* where it is prefetching items and attaching them, but not laying them out/drawing. This should be simple to fix, just need to work out what signals to use. Created #202