LibCore: Introduce a C_OBJECT macro.

This macro goes at the top of every CObject-derived class like so:

class SomeClass : public CObject {
    C_OBJECT(SomeClass)
public:
    ...

At the moment, all it does is create an override for the class_name() getter
but in the future this will be used to automatically insert member functions
into these classes.

Servers/WindowServer/WSWindowSwitcher.h

@@ -10,6 +10,7 @@ class WSKeyEvent;
 class WSWindow;
 
 class WSWindowSwitcher : public CObject {
+    C_OBJECT(WSWindowSwitcher)
 public:
     static WSWindowSwitcher& the();