New port: databases/postgresql-mysql_fdw

This PostgreSQL extension implements a Foreign Data Wrapper (FDW) for MySQL.
The following enhancements are added to the mysql_fdw:
Write-able FDW
Connection Pooling
Where clause push-down
Column push-down
Prepared Statment
Please note that this version of mysql_fdw works with PostgreSQL 9.3, 9.4, 9.5
and 9.6.

WWW: https://github.com/EnterpriseDB/mysql_fdw

PR: 219636
Submitted by: Jov <amutu@amutu.com>