bugfix: fixed compilation with NGINX cores < 1.11.11

A follow-up commit to 947fa00 in which removed the `NGX_LUA_NO_FFI_API`
macro. Doing so prevents the `cln` variable from being declared, which
it previously was before even with such older NGINX core versions.

Author: thibaultcha

src/ngx_http_lua_module.c

@@ -646,9 +646,7 @@ ngx_http_lua_init(ngx_conf_t *cf)
     volatile ngx_cycle_t       *saved_cycle;
     ngx_http_core_main_conf_t  *cmcf;
     ngx_http_lua_main_conf_t   *lmcf;
-#if defined(nginx_version) && (nginx_version >= 1011011)
     ngx_pool_cleanup_t         *cln;
-#endif
     ngx_str_t                   name = ngx_string("host");
 
     if (ngx_process == NGX_PROCESS_SIGNALLER || ngx_test_config) {