Graby: Use consistent arguments for idn_to_ascii across PHP versions

As per <https://www.php.net/manual/en/function.idn-to-ascii.php>, PHP 7.2 deprecated the `INTL_IDNA_VARIANT_2003` constant. But until PHP 7.4, it was still used as the default value of the `$variant` argument and will trigger a deprecation warning (https://github.com/php/php-src/blob/php-7.3.0/ext/intl/idn/idn.c#L318-L320). This in turn broke tests on PHP 7.2 and 7.3:

    1x: idn_to_ascii(): INTL_IDNA_VARIANT_2003 is deprecated
      1x in GrabyTest::testUrlWithAccent from Tests\Graby

This is not an issue on `master` since we require PHP ≥ 7.4 there.

One option would be passing the `INTL_IDNA_VARIANT_UTS46` explicitly to the `$variant` argument so that it is consistent across all supported PHP versions. Unfortunately, this would require raising the requirements to ICU ≥ 4.6, which would break systems that have `intl` extension linked against ancient ICU (allowed on PHP before 7.4: https://github.com/php/php-src/blob/php-7.2.0/ext/intl/idn/idn.c#L85-L87).

Polyfill does support emulating `INTL_IDNA_VARIANT_UTS46` but it will not do anything if the presence of any `intl` extension is detected (https://github.com/symfony/polyfill-intl-idn/blob/v1.26.0/bootstrap.php#L14-L16). So it will not help us when the constant we want does not actually exist.

We could silence the warning with `@` but that is always iffy.

For now, let’s use the polyfill explicitly on PHP 7.2 or 7.3 built with `intl` extension linked against ICU < 4.6. The PHP implementation will be a bit slower but the situation is pretty unlikely in my opinion.

Author: jtojnar

src/Graby.php

@@ -19,6 +19,7 @@
 use Readability\Readability;
 use Smalot\PdfParser\Parser as PdfParser;
 use Symfony\Component\OptionsResolver\OptionsResolver;
+use Symfony\Polyfill\Intl\Idn\Idn as SymfonyIdn;
 
 /**
  * @todo add proxy
@@ -491,7 +492,15 @@ private function validateUrl($url)
         $uri = new Uri((string) $url);
 
         if (preg_match('/[\x80-\xff]/', $uri->getHost())) {
-            $uriIdnSafe = idn_to_ascii($uri->getHost());
+            $uriIdnSafe = \defined('INTL_IDNA_VARIANT_UTS46') ? idn_to_ascii(
+                $uri->getHost(),
+                \IDNA_DEFAULT,
+                \INTL_IDNA_VARIANT_UTS46
+            ) : SymfonyIdn::idn_to_ascii(
+                $uri->getHost(),
+                SymfonyIdn::IDNA_DEFAULT,
+                SymfonyIdn::INTL_IDNA_VARIANT_UTS46
+            );
 
             if (false === $uriIdnSafe) {
                 throw new \InvalidArgumentException(\sprintf('Url "%s" is not valid IDN to ascii.', $url));