LibCore: Put all classes in the Core namespace and remove the leading C

I've been wanting to do this for a long time. It's time we start being
consistent about how this stuff works.

The new convention is:

- "LibFoo" is a userspace library that provides the "Foo" namespace.

That's it :^) This was pretty tedious to convert and I didn't even
start on LibGUI yet. But it's coming up next.

Libraries/LibCore/CLocalServer.h

@@ -29,27 +29,31 @@
 #include <LibCore/CNotifier.h>
 #include <LibCore/CObject.h>
 
-class CLocalSocket;
+namespace Core {
 
-class CLocalServer : public CObject {
-    C_OBJECT(CLocalServer)
+class LocalSocket;
+
+class LocalServer : public Object {
+    C_OBJECT(LocalServer)
 public:
-    virtual ~CLocalServer() override;
+    virtual ~LocalServer() override;
 
     bool take_over_from_system_server();
     bool is_listening() const { return m_listening; }
     bool listen(const String& address);
 
-    RefPtr<CLocalSocket> accept();
+    RefPtr<LocalSocket> accept();
 
     Function<void()> on_ready_to_accept;
 
 private:
-    explicit CLocalServer(CObject* parent = nullptr);
+    explicit LocalServer(Object* parent = nullptr);
 
     void setup_notifier();
 
     int m_fd { -1 };
     bool m_listening { false };
-    RefPtr<CNotifier> m_notifier;
+    RefPtr<Notifier> m_notifier;
 };
+
+}