Ensure that WINVER is defined early enough, so other system headers
won't fall back to their default value. Specifically, this solves a
build failure (-Werror) with mingw-w64 ("WINVER redefined").
When you pass the flag AI_ADDRCONFIG to getaddrinfo(), it does not
consider address families on the loopback device. When run on a
machine without an external network card, just with "lo", it was
unable to look up any address.
