New port: databases/plpgsql_check

Plpgsql_check is next generation of plpgsql_lint. It allows to check source
code by explicit call plpgsql_check_function. The SQL statements inside
PL/pgSQL functions are checked by validator for semantic errors. These errors
can be found by plpgsql_check_function. PostgreSQL 9.2 is required, PostgreSQL
9.3, 9.4, 9.5, 9.6 and 10 are supported.

WWW: https://github.com/okbob/plpgsql_check

PR: 219680
Submitted by: Jov <amutu@amutu.com>