neverbleed: fix compilation when lacking engine

Slight modification of PR/28
h2o#28

Author: phoepsilonix

neverbleed.c

@@ -2233,6 +2233,7 @@ int neverbleed_init(neverbleed_t *nb, char *errbuf)
         EC_KEY_METHOD_set_sign(ecdsa_method, ecdsa_sign_proxy, NULL, NULL);
 #endif
 
+#ifndef OPENSSL_NO_ENGINE
         if ((nb->engine = ENGINE_new()) == NULL || !ENGINE_set_id(nb->engine, "neverbleed") ||
             !ENGINE_set_name(nb->engine, "privilege separation software engine") || !ENGINE_set_RSA(nb->engine, rsa_method)
 #ifdef NEVERBLEED_ECDSA
@@ -2243,6 +2244,7 @@ int neverbleed_init(neverbleed_t *nb, char *errbuf)
             goto Fail;
         }
         ENGINE_add(nb->engine);
+#endif
     }
 #endif
 
@@ -2263,7 +2265,9 @@ int neverbleed_init(neverbleed_t *nb, char *errbuf)
     if (listen_fd != -1)
         close(listen_fd);
     if (nb->engine != NULL) {
+#ifndef OPENSSL_NO_ENGINE
         ENGINE_free(nb->engine);
+#endif
         nb->engine = NULL;
     }
     return -1;