[monitor.c monitor.h servconf.c servconf.h sshd.c sshd_config.5 sshd_config]
Support logging via monitor process using a LogViaMonitor option. It
makes the post-auth privsep slave log via a socketpair shared with
the monitor, based on pre-auth privsep slave log code.
[log.c log.h session.c]
don't reset log handler where LogViaMonitor is enabled
[sftp-server-main.c sftp-server.c sftp.h]
allow sftp-interanl to log via its monitor process