Libraries: Create top level directory for libraries.

Things were getting a little crowded in the project root, so this patch
moves the Lib*/ directories into Libraries/.

Libraries/LibGUI/GApplication.h

@@ -0,0 +1,38 @@
+#pragma once
+
+#include <AK/Badge.h>
+#include <AK/HashMap.h>
+#include <AK/OwnPtr.h>
+#include <LibGUI/GShortcut.h>
+
+class GAction;
+class GKeyEvent;
+class GEventLoop;
+class GMenuBar;
+class Point;
+
+class GApplication {
+public:
+    static GApplication& the();
+    GApplication(int argc, char** argv);
+    ~GApplication();
+
+    int exec();
+    void quit(int = 0);
+
+    void set_menubar(OwnPtr<GMenuBar>&&);
+    GAction* action_for_key_event(const GKeyEvent&);
+
+    void register_global_shortcut_action(Badge<GAction>, GAction&);
+    void unregister_global_shortcut_action(Badge<GAction>, GAction&);
+
+    void show_tooltip(const StringView&, const Point& screen_location);
+    void hide_tooltip();
+
+private:
+    OwnPtr<GEventLoop> m_event_loop;
+    OwnPtr<GMenuBar> m_menubar;
+    HashMap<GShortcut, GAction*> m_global_shortcut_actions;
+    class TooltipWindow;
+    TooltipWindow* m_tooltip_window { nullptr };
+};