Zend\Validator tests refactoring

[gianarb]

Time: 11.36 seconds, Memory: 76.00Mb
There were 4 errors:
1) ZendTest\Validator\EmailAddressTest::testMXRecords
constant(): Couldn't find constant TESTS_ZEND_VALIDATOR_ONLINE_ENABLED

/home/gianarb/git/zf2/tests/ZendTest/Validator/EmailAddressTest.php:303
........
FAILURES!
Tests: 1436, Assertions: 3068, Errors: 4, Incomplete: 5.

This test failed because

if (!constant('TESTS_ZEND_VALIDATOR_ONLINE_ENABLED')) {
    $this->markTestSkipped('Testing MX records has been disabled');
}

I'm replacing them with

if (!defined('TESTS_ZEND_VALIDATOR_ONLINE_ENABLED')) {
    $this->markTestSkipped('Testing MX records has been disabled');
}

[Pittiplatsch]

if (
    !defined('TESTS_ZEND_VALIDATOR_ONLINE_ENABLED')
    || !constant('TESTS_ZEND_VALIDATOR_ONLINE_ENABLED')
) {
    $this->markTestSkipped('Testing MX records has been disabled');
}

[Ocramius]

Handled in #6943