Fix hellowindow example

It seems this example never worked as expected.
It has a 'multiple' option which should show extra
windows with rendering taking place in different
thread, however although render is moved to other thread
render() function was never called in that thread.

Fix following things:
 * make rendering in other thread
 * stop requestUpdate if nothing is exposed
 * add timer so animation works at the same speed despite
   of number of windows (renderer B renders two windows)
 * wait for render to finish before triggering requestUdpate
 * remove mutex where not needed

Pick-to: 5.15
Change-Id: I420436bd28d0357534332dd55b088d634d906c14
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

0 files changed, 0 insertions, 0 deletions