fixed a coding style issue: we did not declare C variables at the beginning of the current code block in ngx_http_lua_del_thread, reported by runner-mei in github issue openresty#93.

Author: agentzh

src/ngx_http_lua_util.c

@@ -217,14 +217,15 @@ ngx_http_lua_del_thread(ngx_http_request_t *r, lua_State *L, int ref,
         int force_quit)
 {
     ngx_http_lua_ctx_t  *ctx;
+    lua_State           *cr;
 
     ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
             "lua deleting thread");
 
     lua_getfield(L, LUA_REGISTRYINDEX, NGX_LUA_CORT_REF);
 
     lua_rawgeti(L, -1, ref);
-    lua_State *cr = lua_tothread(L, -1);
+    cr = lua_tothread(L, -1);
     lua_pop(L, 1);
 
     dd("cr: %p, force quit: %d", cr, (int) force_quit);