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.

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.

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

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

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

It's not present in -W -Wall -Wextra on OpenBSD but it is enabled on other systems.

Incorporate the OpenSMTPD' privsep crypto engine. The idea behind it is to never load the certificate' private keys in a networked process, instead they are loaded in a separate process (the `crypto' one) which signs payloads on the behalf of the server processes. This way, we greatly reduce the risk of leaking the certificate' private key should the server process be compromised. This currently compiles only on LibreSSL (portable fix is in the way).

We don't always do privilege dropping (as we may start as unprivileged user), so set these two beforehand so when we skip privdrop we don't miss to set privsep_process and set the process' title.