Make QQuickWindow::forcePolish() private.
Make QQuickWindow::forcePolish() private.

Adding public API was not the intention when adding
this slot.

Change-Id: If477917c434b32d5e5cd1fa6c640f1a6b167dd24
Reviewed-by: Shawn Rutledge <7b40856c8c1100512025516d7c58756d644d9e8d@digia.com>

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