unix: getaddrinfo_cb status arg should be 0 or -1

The documentation in uv.h states that the status argument to the
uv_getaddrinfo() callback is either 0 or -1 but uv-unix actually
passed it the addrinfo error code. Rectify that and add a regression
test.

Fixes #754.
unix, windows: remove ngx-queue.h

Avoids an extra #include in public headers and stops the ngx_queue_*
types and macros from leaking into user code.