openssl: define a startup-hook so that openssl initializes automatically

Fix for the remaining problem in #1009. I think it is ok to depend on openssl being available.. In the future it would be nice if Factor had hooks for vocab loading. Then you could write something like `[ init-ssl ] "openssl" add-vocab-load-hook` and the quotation would be ran once, when the vocab was first imported. But  alas, I couldn't find any hook like that.