QCoreApplication: Add static setter for application file path.

In cases where QGuiApplication is instantiated by a library
embedded into another application via some plugin mechanism
(for example, Active X controls built using Qt), the QPA platform plugin
and other plugins cannot be found next to the application executable.
In this case, the library should set the application file path to
its deployment location such that plugin paths are set accordingly,
the directory is added to the path and qt.conf is found, should it exist.

Task-number: QTBUG-34989

Change-Id: I4a53104b5121a8d26751129912f999228be45dfd
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>
Fix test compilation on WinRT

Tweak a handful of tests which didn't compile on this platform.

Change-Id: I208d9eb289dfb226746c6d0163c3ea752485033b
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@digia.com>