Ask the Preferences Widget to show and be visible

The 'show' call only makes the dialog visible, but if it's
covered by any other window that's not from *this* program
it could still be hidden in some OSes. the call to raise()
asks the window manager to make the widget to be on top of the
widget stack.

Signed-off-by: Tomaz Canabrava <tomaz.canabrava@intel.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

qt-ui/mainwindow.cpp

@@ -589,6 +589,7 @@ void MainWindow::showProfile()
 void MainWindow::on_actionPreferences_triggered()
 {
 	PreferencesDialog::instance()->show();
+	PreferencesDialog::instance()->raise();
 }
 
 void MainWindow::on_actionQuit_triggered()