Fix compilation errors when building without SSL

lib/sslgen.c

@@ -400,11 +400,16 @@ void Curl_ssl_close(struct connectdata *conn)
 CURLcode Curl_ssl_shutdown(struct connectdata *conn, int sockindex)
 {
   if(conn->ssl[sockindex].use) {
+#ifdef USE_SSLEAY
+    return Curl_ossl_shutdown(conn, sockindex);
+#else
 #ifdef USE_GNUTLS
     return Curl_gtls_shutdown(conn, sockindex);
 #else
-    return Curl_ossl_shutdown(conn, sockindex);
-#endif
+    (void)conn;
+    (void)sockindex;
+#endif /* USE_GNUTLS */
+#endif /* USE_SSLEAY */
   }
   return CURLE_OK;
 }