dns,http,sa: fix HAVE_INET6 off warnings (#219)

fixes #216

src/dns/client.c

@@ -856,7 +856,10 @@ int dnsc_alloc(struct dnsc **dcpp, const struct dnsc_conf *conf,
 	       const struct sa *srvv, uint32_t srvc)
 {
 	struct dnsc *dnsc;
-	struct sa laddr, laddr6;
+	struct sa laddr;
+#ifdef HAVE_INET6
+	struct sa laddr6;
+#endif
 	int err;
 
 	if (!dcpp)

src/http/client.c

@@ -1113,5 +1113,8 @@ void http_client_set_laddr6(struct http_cli *cli, const struct sa *addr)
 #ifdef HAVE_INET6
 	if (cli && addr)
 		sa_cpy(&cli->laddr6, addr);
+#else
+	(void)cli;
+	(void)addr;
 #endif
 }

src/sa/sa.c

@@ -703,6 +703,8 @@ void sa_set_scopeid(struct sa *sa, uint32_t scopeid)
 		return;
 
 	sa->u.in6.sin6_scope_id = scopeid;
+#else
+	(void)scopeid;
 #endif
 }