Drop PDO DB2 driver

UPGRADE.md

 # Upgrade to 3.0
 
+## BC BREAK: Removed PDO DB2 driver
+
+This PDO-based IBM DB2 driver (built on top of pdo_ibm extension) has already been unsupported as of 2.5, it has now been now removed.
+
+The following class has been removed:
+
+ * `Doctrine\DBAL\Driver\PDOIbm\Driver`
+
 ## BC BREAK: Removed support for SQL Anywhere 12 and older
 
 DBAL now requires SQL Anywhere 16 or newer, support for unmaintained versions has been dropped.

lib/Doctrine/DBAL/Driver/PDOIbm/Driver.php

-<?php
-
-namespace Doctrine\DBAL\Driver\PDOIbm;
-
-use Doctrine\DBAL\Driver\AbstractDB2Driver;
-use Doctrine\DBAL\Driver\PDOConnection;
-
-/**
- * Driver for the PDO IBM extension.
- */
-class Driver extends AbstractDB2Driver
-{
-    /**
-     * {@inheritdoc}
-     */
-    public function connect(array $params, $username = null, $password = null, array $driverOptions = [])
-    {
-        return new PDOConnection(
-            $this->_constructPdoDsn($params),
-            $username,
-            $password,
-            $driverOptions
-        );
-    }
-
-    /**
-     * Constructs the IBM PDO DSN.
-     *
-     * @param mixed[] $params
-     *
-     * @return string The DSN.
-     */
-    private function _constructPdoDsn(array $params)
-    {
-        $dsn = 'ibm:';
-        if (isset($params['host'])) {
-            $dsn .= 'HOSTNAME=' . $params['host'] . ';';
-        }
-        if (isset($params['port'])) {
-            $dsn .= 'PORT=' . $params['port'] . ';';
-        }
-        $dsn .= 'PROTOCOL=TCPIP;';
-        if (isset($params['dbname'])) {
-            $dsn .= 'DATABASE=' . $params['dbname'] . ';';
-        }
-
-        return $dsn;
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getName()
-    {
-        return 'pdo_ibm';
-    }
-}

tests/Doctrine/Tests/DBAL/Driver/PDOIbm/DriverTest.php

-<?php
-
-namespace Doctrine\Tests\DBAL\Driver\PDOIbm;
-
-use Doctrine\DBAL\Driver\PDOIbm\Driver;
-use Doctrine\Tests\DBAL\Driver\AbstractDB2DriverTest;
-
-class DriverTest extends AbstractDB2DriverTest
-{
-    public function testReturnsName()
-    {
-        self::assertSame('pdo_ibm', $this->driver->getName());
-    }
-
-    protected function createDriver()
-    {
-        return new Driver();
-    }
-}