add cast in test/x509aux.c preventing compiler warning for VC-WIN64A architecture

Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NMatt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6217)

test/x509aux.c

@@ -161,6 +161,6 @@ int setup_tests(void)
         return 0;
     }
 
-    ADD_ALL_TESTS(test_certs, n);
+    ADD_ALL_TESTS(test_certs, (int)n);
     return 1;
 }