Events: fixed null pointer dereference with resolver and poll. A POLLERR signalled by poll() without POLLIN/POLLOUT, as seen on Linux, would generate both read and write events, but there's no write event handler for resolver events. A fix is to only call event handler of an active event.

# Copyright (C) Igor Sysoev
# Copyright (C) Nginx, Inc.


cat << END >> $NGX_AUTO_CONFIG_H

#ifndef $have
#define $have  $value
#endif

END