refactor link_bc() for GNUnet_memcmp

src/lib/testing_api_cmd_refresh.c

@@ -591,9 +591,8 @@ link_cb (void *cls,
     /* check that the coins match */
     for (unsigned int i=0;i<num_coins;i++)
       for (unsigned int j=i+1;j<num_coins;j++)
-	if (0 == memcmp
-          (&coin_privs[i], &coin_privs[j],
-           sizeof (struct TALER_CoinSpendPrivateKeyP)))
+        if (0 == GNUNET_memcmp
+            (&coin_privs[i], &coin_privs[j]))
           GNUNET_break (0);
     /* Note: coins might be legitimately permutated in here... */
     found = 0;