Add note to QQuickItem docs about directly setting properties in C++.

It's not obvious that calling setPosition() directly, for example,
won't trigger animations defined in behaviors that react to that
item's x and y properties changing, because a quick glance at the
code shows that they have almost identical code paths and both
emit geometryChanged().

Change-Id: Ic7f7019b1bbba24732569c0de777ee02d79c1d3b
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>
Fix line ending for test file

Task-number: QTBUG-40574
Change-Id: If1fcc4cb00c8e477b3afff92eb4a3099424fcfa6
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reduce memory pressure on the JS stack during garbage collection

As the example in QTBUG-42051 demonstrates, QML may produce a lot of binding
objects and each of them produce a QV4::Persistent. During the mark phase we
may run out of JS stack space. One fix (for the future) is to reduce the number
of QV4::Persistent objects, but in the meantime we can also reduce the pressure
on the stack by draining it earlier.

Task-number: QTBUG-42051
Change-Id: Iea73f8a869048ea0bf3f4a64dbd24b6fb8c68f6b
Reviewed-by: Ulf Hermann <ulf.hermann@digia.com>