Match localnetwork is not supported on Windows (no getifaddrs in win32compat)

Summary

The ssh_config Match localnetwork criterion is not supported on Windows. It never matches, and with -v logs:

match localnetwork: not supported on this platform

Version

OpenSSH_for_Windows_10.0p2 (and earlier).

Cause

check_match_ifaddrs() in readconf.c is gated on HAVE_IFADDRS_H, which the Windows build (contrib/win32/openssh/config.h.vs) does not define, and contrib/win32/win32compat/ provides no getifaddrs(). So the #else branch ("not supported on this platform") is compiled in. The same gate disables the getifaddrs() path used by BindInterface in sshconnect.c.

Repro

ssh_config:

Match localnetwork 127.0.0.0/8
    Compression yes

ssh -G -F <cfg> somehost -> compression stays no.

Fix

Implemented in PowerShell/openssh-portable#859: a getifaddrs()/freeifaddrs() shim over the Win32 GetAdaptersAddresses() API, HAVE_IFADDRS_H defined, build wiring, and a unit test. Built and verified on Windows x64 (also cross-compiles for ARM64).

Review check_match_ifaddrs() in readconf.c and the BindInterface path in sshconnect.c, then inspect contrib/win32/openssh/config.h.vs and contrib/win32/win32compat/. Run the Windows unit test mentioned in the issue; done means localnetwork matching and BindInterface work on Windows, with the build verified for x64 and ARM64.