Add REHASH SSLD (admins only) that starts new sslds and marks the
existing ones as inactive until all their clients disconnect.
Very useful whenever the SSL library has a vulnerability because
new connections can use a new version of the library without
disconnecting existing clients/servers.
Add STATS S (admins only) to list ssld processes, status, and client
count.
This backports the code responsible for SPKI digests from release/4.
It also adjusts doc/reference.conf to note that SPKI digests are now
supported, and how to generate them. It does NOT backport the mkfingerprint
program -- the instructions in reference.conf are sufficient. I am ofcourse
open to anyone else backporting the program, but I don't see the need.
