simplify check brought to my attention by gcc who isn't smart enough to figure out that `ret' is always set.

enable -Werror on CI -Wno-deprecated-declarations is needed because of OpenSSL 3 (and macos stupidly deprecating daemon(3) in favour of that trash of posix_spawn.)

drop questionable #warning

rework the configure script now it resembles less oconfigure and more the configure scripts I'm using in my recent projects. I'd argue it's more easy to use it.

avoid arithmetic on void pointers (GNU extension) not really sold on this one, I don't see what other interpretation could be given, but it's not standard so...

add mac_task with disabled runtime tests for the time being the runtime tests fails on the ci (gg: Connection refused); will be revisited after we get a real `listen on' directive.

fix the build with some yacc implementations

remove regress/sha we can use cmp to tell if two files are different, which also has the benefit of being available everywhere and reporting the byte offset of the first difference. Reduces the test dependencies on some systems.

work around missing SOCK_NONBLOCK/CLOEXEC on macos

use the default prefork in tests

load_ca: get a buffer instead of a fd We dup(1) the ca fd and send it to various processes, so they fail loading it. Instead, use load_file to get a buffer with the file content and pass that to load_ca which then loads via BIO.

simplify config_send_kp: use config_send_file

remove proc_ispeer() unused, and was dropped by other copies of proc.c; reduces the diff with httpd' proc.c.

disable the privsep crypto engine on !OpenBSD it fails bandly at runtime on various linux distros and on freebsd. Until a fix is found, disable it so I can move forward.

remove has_siginfo and wrap siginfo behind #ifdef SIGINFO. avoids some warnings in !BSD.