Restored ngx_event_aio_t layout for debug logging.
Restored ngx_event_aio_t layout for debug logging.

The "fd" field should be after 3 pointers for ngx_event_ident() to use it.
This was broken by ccad84a174e0.  While it does not seem to be currently used
for aio-related events, it should be a good idea to preserve the correct
layout nevertheless.

hy0kl/nginx,hy0kl/nginx,hy0kl/nginx