ifdef Q_?S_* cleanup

- clear up some Q_OS_LINUX vs. Q_OS_UNIX
- clear up Q_WS_* vs. Q_OS_* (relatively theoretical exercise)
- use proper #if-#else cascades instead of free-standing #ifs

src/plugins/coreplugin/actionmanager/actionmanager.cpp

@@ -361,7 +361,7 @@ Command *ActionManagerPrivate::registerOverridableAction(QAction *action, const
         baseAction->setEnabled(false);
         baseAction->setObjectName(id);
         baseAction->setParent(m_mainWnd);
-#ifdef Q_OS_MAC
+#ifdef Q_WS_MAC
         baseAction->setIconVisibleInMenu(false);
 #endif
         a->setAction(baseAction);