CLEANUP: cttproxy: remove a warning on undeclared close()

This one is harmless and only happens on old systems anyway.

src/cttproxy.c

@@ -16,6 +16,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 
 #include <sys/socket.h>
 #include <sys/stat.h>