Clang 5.0 fixes

- Added override keyword
- Removed inherited member variables

src/OSSupport/ServerHandleImpl.h

@@ -39,7 +39,7 @@ class cServerHandleImpl:
 
 public:
 	/** Closes the server, dropping all the connections. */
-	~cServerHandleImpl();
+	virtual ~cServerHandleImpl() override;
 
 	/** Creates a new server instance listening on the specified port.
 	Both IPv4 and IPv6 interfaces are used, if possible.

src/OSSupport/TCPLinkImpl.h

@@ -44,7 +44,7 @@ public:
 	cTCPLinkImpl(evutil_socket_t a_Socket, cCallbacksPtr a_LinkCallbacks, cServerHandleImplPtr a_Server, const sockaddr * a_Address, socklen_t a_AddrLen);
 
 	/** Destroys the LibEvent handle representing the link. */
-	~cTCPLinkImpl();
+	virtual ~cTCPLinkImpl() override;
 
 	/** Queues a connection request to the specified host.
 	a_ConnectCallbacks must be valid.

src/OSSupport/UDPEndpointImpl.h

@@ -35,7 +35,7 @@ public:
 	If a_Port is 0, the OS is free to assign any port number it likes to the endpoint. */
 	cUDPEndpointImpl(UInt16 a_Port, cUDPEndpoint::cCallbacks & a_Callbacks);
 
-	~cUDPEndpointImpl();
+	virtual ~cUDPEndpointImpl() override;
 
 	// cUDPEndpoint overrides:
 	virtual void Close(void) override;