Add missing bracket in EGD seeding code.

When configured --with-prngd-socket the code had a missing bracket after
an API change.  Fix that and a couple of warnings.  bz#3032 , from
ole.weidner at protonmail.ch

entropy.c

@@ -201,14 +201,15 @@ rexec_send_rng_seed(struct sshbuf *m)
 void
 rexec_recv_rng_seed(struct sshbuf *m)
 {
-	u_char *buf = NULL;
+	const u_char *buf = NULL;
 	size_t len = 0;
 	int r;
 
-	if ((r = sshbuf_get_string_direct(m, &buf, &len)) != 0
+	if ((r = sshbuf_get_string_direct(m, &buf, &len)) != 0)
 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
 
-	debug3("rexec_recv_rng_seed: seeding rng with %u bytes", len);
+	debug3("rexec_recv_rng_seed: seeding rng with %lu bytes",
+	    (unsigned long)len);
 	RAND_add(buf, len, len);
 }
 #endif /* OPENSSL_PRNG_ONLY */