Force QFileSystemWatcher to use its polling engine

On Linux, QFileSystemWatcher will use inotify if available. However, inotify doesn't support notifications for changes to files on network mounts (for instance, an NFS mounted directory).

QFileSystemWatcher contains a polling engine, which would solve this problem. However, there is no public API to force QFileSystemWatcher to use its polling engine, nor does it auto-detect whether a file is on an NFS share or not.

The ideal solution would be for Qt to detect whether a file is "supported" by inotify and fall back on its polling engine only for non-supported file locations. I don't know whether that's possible however. Another solution would be to provide a public API to force the use of the poller engine.

Note: you can force QFileSystemWatcher to use the poller engine using watcher.setObjectName(QLatin1String("_qt_autotest_force_engine_poller"));, but this is not in the public API so it may break with future releases (works with 4.6.0).