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).

Don't have all the processes read gmid.conf. The parent needs to do that, and the will send the config to the children (already happening.) The other processes were reading the config anyway to figure out the user and the chroot (if enabled); make the parent pass additional flag to propagate that info. We dissociate a bit from the "usual" proc.c but it's a change worth having.

this avoids having the daemon dieing on SIGHUP with a bad config file.

while here also make them a list rather than a fixed-size array.

set them as global vars; rename foreground -> debug

so that ge can provide its own log_request without requiring a separate logger process.

It uses the 'common' proc.c from various OpenBSD-daemons. gmid grew organically bit by bit and it was also the first place where I tried to implement privsep. It wasn't done very well, in fact the parent process (that retains root privileges) just fork()s a generation of servers, all sharing *exactly* the same address space. No good! Now, we fork() and re-exec() ourselves, so that each process has a fresh address space. Some features (require client ca for example) are temporarly disabled, will be fixed in subsequent commits. The "ge" program is also temporarly disabled as it needs tweaks to do privsep too.