New port: databases/jlog

JLog is short for "journaled log" and this package is really an API
and implementation that is libjlog. What is libjlog? libjlog is a
pure C, very simple durable message queue with multiple subscribers
and publishers (both thread and multi-process safe). The basic
concept is that publishers can open a log and write messages to it
while subscribers open the log and consume messages from it. "That
sounds easy." libjlog abstracts away the need to perform log rotation
or maintenance by publishing into fixed size log buffers and
eliminating old log buffers when there are no more consumers pending.

WWW: https://labs.omniti.com/labs/jlog

Reviewed by: brnrd