Ensured that a virtual destructor is declared, so that the various automatically-generated real constructors get in on the action.

Machines/AmstradCPC/AmstradCPC.cpp

@@ -881,3 +881,5 @@ using namespace AmstradCPC;
 Machine *Machine::AmstradCPC() {
 	return new AmstradCPC::ConcreteMachine;
 }
+
+Machine::~Machine() {}

Machines/AmstradCPC/AmstradCPC.hpp

@@ -52,6 +52,8 @@ class Machine:
 	public ConfigurationTarget::Machine,
 	public KeyboardMachine::Machine {
 	public:
+		virtual ~Machine();
+
 		/// Creates an returns an Amstrad CPC on the heap.
 		static Machine *AmstradCPC();