turn status into an u_int16_t
epoll improvements.

* check for EPOLLRDHUP
* in kore_platform_schedule_read() don't use EPOLLET
Introduce a wait queue for our pgsql code.

Instead of letting http_requests spin, if we cannot allocate
a connection for the request we will queue them up put them to sleep.

When a connection becomes available, we'll wake up a request that
was waiting for a connection and let it continue.

This completely avoids consuming massive amounts of cpu time
when dealing with thousands of requests waiting for a pgsql
worker to become ready.