“Lightbulb Sun” bugfix release

signify(1) pubkeys for this release: RWTy3UJQzpxBUAymBwb2EGLLm0b3H/1n8hzhaC9HYFYzNuTavGt9QSwC

(note: no aarch64 precompiled binaries this time)

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 @chilledfrogs.
• configure script: allow to set MANDIR from cmdline (@chilledfrogs)
• add systemd-sysusers sample file in contrib/ (@eniehack )
• [linux/seccomp] allow fstatat64(2), llseek(2) and sigreturn(2), needed by glibc on armv7. (@Toby222)
• [linux/seccomp] tightens rules by allowing openat(2) only with the O_RDONLY flag.