Add ProcessBuilder::setPrefix method
Modify Request::getClientIp() to use IpUtils::checkIp()

Adds the ability to use CIDR notation in the trusted proxy list
Allow setting trusted_proxies using CIDR notation
[HttpFoundation] added some unit tests for ranges of trusted IP addresses
[HttpFoundation] refactored code to avoid code duplication
[HttpFoundation] updated CHANGELOG
merged branch fabpot/trusted-proxies (PR #7735)

This PR was merged into the master branch.

Discussion
----------

[HttpFoundation][FrameworkBundle] Add CIDR notation support in trusted proxy list

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #7312, #7262
| License       | MIT
| Doc PR        | symfony/symfony-docs#2287

Should be rebased once #7734 is merged.

Commits
-------

7b32794 [HttpFoundation] updated CHANGELOG
e7c1696 [HttpFoundation] refactored code to avoid code duplication
1695067 [HttpFoundation] added some unit tests for ranges of trusted IP addresses
811434f Allow setting trusted_proxies using CIDR notation
ddc9e38 Modify Request::getClientIp() to use IpUtils::checkIp()
merged branch romainneutron/process-builder-prefix (PR #7584)

This PR was merged into the master branch.

Discussion
----------

[Process] Add ProcessBuilder::setPrefix method

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT

This introduce a new feature for the `ProcessBuilder` that allows to prefix all generated `Process` commands with a custom value.
This is mostly useful when dealing with binary drivers.

Use case :

```php
use Symfony\Component\Process\ExecutableFinder;
use Symfony\Component\Process\ProcessBuilder;

class PhpDriver
{
    private $pb;

    public function __construct(ProcessBuilder $pb)
    {
        $this->pb = $pb;
    }

    public function getInfos()
    {
        return $this->execute('-i');
    }

    public function getVersion()
    {
        return $this->execute('-v');
    }

    private function execute(array $arguments)
    {
        return $this
            ->pb
            ->setArguments($arguments)
            ->createProcess()
            ->run()
            ->getOutput();
    }
}

$finder = new ExecutableFinder();

$pb = new ProcessBuilder();
$pb->setPrefix($finder->find('php'));

$driver = new PhpDriver($pb);
$driver->getVersion();
$driver->getInfos();
```

Commits
-------

cab53ee Add ProcessBuilder::setPrefix method