[Finder] Added support for GLOB patterns in the directories passed to the in() method.

Pattern has to resolve to at least one directory, otherwise exception is thrown (just like when path to an invalid directory is passed).
merged branch jakzal/finder-glob-support (PR #6531)

This PR was merged into the master branch.

Commits
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29b9611 [Finder] Added support for GLOB patterns in the directories passed to the in() method.

Discussion
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[Finder] Added support for wildcard characters (GLOB patterns)

Added support for wildcard characters in the paths passed to the *in()* method. Each pattern has to resolve to at least one directory, otherwise exception is thrown (just like when path to an invalid directory is passed).

Example usage:

```php
$finder = new \Symfony\Component\Finder\Finder();
$files = $finder->files()
    ->name('validators.en.*')
    ->in(array(
        'src/Symfony/*/*/Resources/translations',
    ));

foreach ($files as $file) {
    var_dump($file->getRealPath());
}
```

Bug fix: no
Feature addition: yes
Backwards compatibility break: no
Symfony2 tests pass: yes
Fixes the following tickets: #5450
Todo: -
License of the code: MIT
Documentation PR: symfony/symfony-docs#2089