Import repmgr-4.0.1 as databases/repmgr

Based on package provided by Matthieu Guegan in joyent/pkgsrc#49

repmgr is a suite of open-source tools to manage replication and failover
within a cluster of PostgreSQL servers.  It enhances PostgreSQL's built-in
replication capabilities with utilities to set up standby servers, monitor
replication, and perform administrative tasks such as failover or
switchover operations.

(jperkin)