Update windowsaio for changes to the thread structure

The free/busy/requeue list has been replaced with a FIFO + ring: update
windowsaio.c to work with the new code.

Modified by Jens to check for IO_U_F_FLIGHT before doing engine
private checks.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
posix_fadvise is now provided in helpers.c: remove it from the Windows posix.c

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Windows: include winsock2.h instead of windows.h to avoid a warning.

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