Fix-up after commit of Bug#11900714

The patch fixes a build problem on MacOSX, where
the compiler complains about unused parameters.

mysys/my_net.c

@@ -112,8 +112,10 @@ extern pthread_mutex_t LOCK_gethostbyname_r;
 */
 
 struct hostent *my_gethostbyname_r(const char *name,
-				   struct hostent *result, char *buffer,
-				   int buflen, int *h_errnop)
+				   struct hostent *result __attribute__((unused)),
+                                   char *buffer __attribute__((unused)),
+				   int buflen __attribute__((unused)),
+                                   int *h_errnop)
 {
   struct hostent *hp;
   pthread_mutex_lock(&LOCK_gethostbyname_r);