Does not compile with OpenSSL 3; issues related to deprecated libxml2 use

[ngie-eign]

The package fails to build against OpenSSL 3. Moreover, there are a variety of issues related to deprecated libxml2 use.
Log originally came from https://pkg.bofh.network/data/MAIN-default-openssl3/2023-05-02_02h56m25s/logs/errors/xar-1.6.1_2.log .
xar-1.6.1_2.log

[grahamperrin]

Cross-reference:

• FreeBSD bug 271193 – archivers/xar: does not compile/link against OpenSSL 3

See also:

• freebsd/freebsd-ports@ebc92ce

[DevX-Cipher]

I've successfully compiled this code and even began porting it to run natively on Windows. This was my first time working with Linux-specific system calls, and I'm pleased with how much progress I've made so far. The application builds and runs on Windows, but currently, the archive it generates is empty. I'm continuing to research and debug the issue to ensure proper file inclusion during archive creation.