iphlpapi: Implement IcmpSendEcho2Ex() using nsiproxy.
This results in a small change in behaviour reflected by the change to
the tests: previously IcmpCreateFile() would fail if neither a
SOCK_RAW nor a SOCK_DGRAM socket were available. With this patch, that
failure is delayed until IcmpSendEcho2Ex(). There's no evidence that
the original behaviour matches Windows; it's likely the tests were
written this way to match Wine's implementation. If there does turn
out to be an app that depends on the old behaviour, it would be
possible to send an ioctl during IcmpCreateFile() to probe for this.
Signed-off-by: Huw Davies <huw@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>