server: fix wrong error return on host lookup failure

Signed-off-by: Jens Axboe <axboe@kernel.dk>
configure: add test for whether required IPv6 helpers

Signed-off-by: Jens Axboe <axboe@kernel.dk>
client/server: don't reset ipv6 expectations

fio_server_parse_host() no longer falls back to ipv4, so just
pass in the actual value, not a reference.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
engine: protect net engine IPv6 support with configure check

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Fix Windows headers for IPv6

MinGW includes all the necessary IPv6 definitions, so include ws2tcpip.h
and remove the custom definitions.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Update Windows build for new threading library

MinGW now uses libwinpthread-1.dll instead of pthreadGC2.dll.
To simplify things, create a static executable so users can run fio
from anywhere without needing to copy the dll.

Signed-off-by: Jens Axboe <axboe@kernel.dk>