Windows: Use Standard Networking Functions If Possible

Windows: Use Standard Networking Functions If Possible

Currently, the Windows code use Winsock2-specific APIs to try to emulate
calls such as inet_pton(), inet_ntop() and if_nametoindex(), which may not
do the job all the time.  On Vista and later, Winsock2 does provide a
proper implementation for these functions, so we can use them if they exist
on the system, by querying for them during g_networking_init().  Otherwise,
we continue to use the original code path for these, in the case of XP and
Server 2003.

This enables many of the network-address tests to pass on Windows as a
result, when the native Winsock2 implementations can be used.

https://bugzilla.gnome.org/show_bug.cgi?id=730352