Say hello to QQuickItem::grabToImage().

[ChangeLog][QtQuick][Item] Added functions QQuickItem::grabToImage()
and Item::grabToImage() to allow grabbing of items into
system-memory images.

Change-Id: I76cd73bb62f7440569c6fce63d63528559845721
Reviewed-by: Michael Brasser <michael.brasser@live.com>
Let render loop be more tolerant wrt when markDirty is called.

Change-Id: I95f1d6fe4695a09b1b6ccaf026137dabc22ec82c
Reviewed-by: Michael Brasser <michael.brasser@live.com>

Conflicts:
	src/quick/scenegraph/coreapi/qsgrenderer_p.h
MER: Remove revision for QQuickItem::grabToImage()

This symbol is from Qt 5.4 (QtQuick 2.4), so we need to make it
accessible for now. Patch can be removed once we're on Qt 5.4.

Change-Id: Ie73c070ac2ec9f6e58dcf6d40ecf27266b61f6ee
Merge pull request #17 from sletta/item-grabber

[qtdeclarative] Item grabber and supporting bugfix