Clean socket shutdown in C version too.

Related to https://github.com/kanaka/noVNC/issues/58 (supporting Apple
Remote Desktop).

other/Makefile

@@ -10,5 +10,5 @@ websocket.o: websocket.c websocket.h
 websockify.o: websockify.c websocket.h
 
 clean:
-	rm -f websockify kumina *.o
+	rm -f websockify *.o
 

other/websockify.c

@@ -267,6 +267,7 @@ void proxy_handler(ws_ctx_t *ws_ctx) {
 
     do_proxy(ws_ctx, tsock);
 
+    shutdown(tsock, SHUT_RDWR);
     close(tsock);
 }