Stop polish-and-sync timer when the window is destroyed
Stop polish-and-sync timer when the window is destroyed

The threaded render loop continues to run the polish-and-sync timer for
ever in case the QQuickWindow is destroyed while the timer is active.
Instead of pumping the timer events on the render thread for ever, the
timer has to be killed somewhere.

Change-Id: I8e458624e26ebfacb6cc69a4f2fbb3da57ae5e0e
Reviewed-by: Gunnar Sletta <d0b71651f3efaa9fda200bbcc395b7b82a871fdd@jollamobile.com>

mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,qmlc/qtdeclarative,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,qmlc/qtdeclarative,qmlc/qtdeclarative,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,qmlc/qtdeclarative,qmlc/qtdeclarative,mgrunditz/qtdeclarative-2d