w32: Fix compilation (wrong include file)

arpa/inet.h is not available for w32, so commit
edbb2136 breaks
w32 compilations.

This is fixed by using qemu_socket.h.

Signed-off-by: Stefan Weil <weil@mail.berlios.de>
Reviewed-by: Alon Levy <alevy@redhat.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>