Today, test_reuseaddr() triggers a buffer overflow when accept()-ing an
IPv6 client due to the supplied peer name buffer (`struct sockaddr`)
being too small to hold an AF_INET6 address (`struct sockaddr_in6`).

Fix this by changing the type of `saddr` from `struct sockaddr` to
`struct sockaddr_storage`.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=54376
(cherry picked from commit 876742bf)