PHPUnit 4.2: Exceptions with chars used by regular expression can break tests

Hey,

we just tried to use PHPUnit 4.2 on our project and ran into a rather tricky problem, from which I've created a simpler example project you can use to test this bug.

https://github.com/dreis2211/phpunit-exception-test

or you try to run this
```php
<?php

class ExampleClass {

    public function doSomething() {
        throw new Exception('[Have you done something wrong? Try again.]');
    }

}

class ExampleClassTest extends PHPUnit_Framework_TestCase {

    public function testExceptionWithQuestionMark() {
        $this->setExpectedException('Exception', '[Have you done something wrong? Try again.]');

        $model = new ExampleClass();
        $model->doSomething();
    }
}
```

This behaviour was most likely introduced with the following commit.
https://github.com/sebastianbergmann/phpunit/commit/f8826506baf9ec673aaf56887a6682093bccffb1

Cheers,

dreis2211