[Oxygen] Use preference icons from theme if available.

src/lib/app/qupzilla.cpp

@@ -385,7 +385,7 @@ void QupZilla::setupMenu()
     m_actionAbout->setMenuRole(QAction::AboutRole);
     connect(m_actionAbout, SIGNAL(triggered()), MENU_RECEIVER, SLOT(aboutQupZilla()));
 
-    m_actionPreferences = new QAction(QIcon(":/icons/faenza/settings.png"), tr("Pr&eferences"), 0);
+    m_actionPreferences = new QAction(QIcon::fromTheme("preferences-desktop", QIcon(":/icons/faenza/settings.png")), tr("Pr&eferences"), 0);
     m_actionPreferences->setMenuRole(QAction::PreferencesRole);
     m_actionPreferences->setShortcut(QKeySequence(QKeySequence::Preferences));
     connect(m_actionPreferences, SIGNAL(triggered()), MENU_RECEIVER, SLOT(showPreferences()));

src/lib/preferences/preferences.cpp

@@ -71,7 +71,7 @@ Preferences::Preferences(QupZilla* mainClass, QWidget* parent)
         ui->listWidget->item(2)->setIcon(QIcon::fromTheme("tab-new-background", QIcon(":/icons/preferences/applications-internet.png")));
         ui->listWidget->item(3)->setIcon(QIcon::fromTheme("preferences-system-network", QIcon(":/icons/preferences/applications-webbrowsers.png")));
         ui->listWidget->item(4)->setIcon(QIcon::fromTheme("preferences-desktop-font", QIcon(":/icons/preferences/applications-fonts.png")));
-        ui->listWidget->item(5)->setIcon(QIcon::fromTheme("preferences-desktop-keyboard-shortcuts", QIcon(":/icons/preferences/preferences-desktop-keyboard-shortcuts.png")));
+        ui->listWidget->item(5)->setIcon(QIcon::fromTheme("configure-shortcuts", QIcon(":/icons/preferences/preferences-desktop-keyboard-shortcuts.png")));
         ui->listWidget->item(6)->setIcon(QIcon::fromTheme("download", QIcon(":/icons/preferences/mail-inbox.png")));
         ui->listWidget->item(7)->setIcon(QIcon::fromTheme("user-identity", QIcon(":/icons/preferences/dialog-password.png")));
         ui->listWidget->item(8)->setIcon(QIcon::fromTheme("preferences-system-firewall", QIcon(":/icons/preferences/preferences-system-firewall.png")));