Fil-C Linux/x86_64+ARM64 version 0.684

This is a bugfix release.

• Fix a compiler bug that causes programs to panic due to alignment checks on code that didn't request that alignment.
• Add support for oversize and misaligned atomics (the ones that are implemented as C runtime calls rather than instructions).
• Fix a compiler bug that causes uninitialized volatile locals to get a fresh zero-initialized allocation after longjmp.

The following updates have been made to /opt/fil:

• OpenSSH updated to 10.5p1 with rebased Linux distro patches (Fedora PQ crypto, Ubuntu config file, GSSAPI kex, and systemd integration). The Fedora PQ patch was fixed so that it uses upstream OpenSSH's code, not OpenSSL's via Fedora changes, whenever possible. Also, mlkem+nistp KEX is disabled by default in sshd (but can be enabled via config files, as Fedora does).
• Added libxml2 and libpq.

Thanks to @dwsteele for contributing to this release!

Guide to the available files:

• filc-0.684-linux-x86_64.tar.xz and filc-0.684-linux-aarch64.tar.xz are the traditional, self-contained "pizfix" distributions for X86_64 and ARM64, respectively. These only include the compiler, doesn't require root, and are based on the musl libc. These distributions are recommended for quickly trying out Fil-C.
• optfil-0.684-linux-x86_64.tar.xz is the /opt/fil distribution, only available for X86_64. It includes many useful programs like OpenSSH, sudo, tmux, and git. It's based on glibc 2.40, and requires root permissions. This is recommended for giving Fil-C deeper scrutiny.