New port: databases/libcouchbase

This is the C client library for Couchbase. It communicates with the cluster
and speaks the relevant protocols necessary to connect to the cluster and
execute data operations.

https://github.com/couchbase/libcouchbase/

PR: 205377
Submitted by: gebhart@secnetix.de, Sergey Avseyev <sergey.avseyev@gmail.com>