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.

add -Wpointer-sign to the mix It's not present in -W -Wall -Wextra on OpenBSD but it is enabled on other systems.

fixes for -Wpointer-sign

cast uint64_t to unsigned long long

work around different signature for ecdsae_compute_key

add a privsep crypto engine 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).

drop useless debug statement