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/LibCore/CNotifier.cpp

@@ -0,0 +1,15 @@
+#include <LibCore/CEvent.h>
+#include <LibCore/CEventLoop.h>
+#include <LibCore/CNotifier.h>
+
+CNotifier::CNotifier(int fd, unsigned event_mask)
+    : m_fd(fd)
+    , m_event_mask(event_mask)
+{
+    CEventLoop::register_notifier({}, *this);
+}
+
+CNotifier::~CNotifier()
+{
+    CEventLoop::unregister_notifier({}, *this);
+}