V4 JIT: tune generated instructions for inplace binops

Generate better code for in-place binary operations where the right-hand
side is either a constant or a memory address. Now that the JIT can do
this, also tell the register allocator not to un-spill that right-hand
side.

Change-Id: I0ab852f6b92f90dfed99c05fbaf91aad2549ecf4
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Write memory events into tracefiles generated by qmlprofiler

Change-Id: Ic01505194f29967ed1aad16fe36e14dc5532ae25
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Remove Item.window

Window is a type in a different import, so we can't just casually use
it in Item. Note that this API was going to be new in the next release,
so it can be safely removed (at least until we do it right).

Change-Id: I9e3eb5f65ea5f46d30fb7905d0f9c479daaccbff
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>
Reviewed-by: Alan Alpert (Personal) <416365416c@gmail.com>
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>