net/gmid: update to 1.8.3

Bug Fixes:

• fix a CGI timing issue: if a connection handled by a CGI scripts is interrupted with the right timing it causes the server process to exit with "fatal in client_by_id: invalid id X".

New Features:

• add a new block `type { ... }' to define mime types mapping.

Improvements:

• use shell built-in `command' instead of which(1), prodded by cage and Allen Sobot.
• configure script: allow to set MANDIR from cmdline (Allen Sobot)
• add systemd-sysusers sample file in contrib/ (Nakaya)
• [linux/seccomp] allow fstatat64(2), llseek(2) and sigreturn(2), needed by glibc on armv7. (Tobias Berger)
• [linux/seccomp] tightens rules by allowing openat(2) only with the O_RDONLY flag.

PR: 262832