Clarify QWindow::format() docs

Change-Id: I35c5f9e7a235afc75c0051b3958875371f182b29
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>
Clarify QOpenGLContext::format() docs

Avoid unrealistic expectations where applications would assume that
requestedFormat() == format().

Change-Id: I12dcfda3d86ce26f1cae9771b1fe2203291864db
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>
Avoid asserting with QQuickWidget on Windows

Change-Id: I8b4185a9725b27b3e3e0e049e3a001ed61bcf1d5
Reviewed-by: Paul Olav Tvete <paul.tvete@digia.com>