minor #2839 Use PHP 7.2 polyfill instead of xml one (keradus)
minor #2839 Use PHP 7.2 polyfill instead of xml one (keradus)

This PR was merged into the 2.2 branch.

Discussion
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Use PHP 7.2 polyfill instead of xml one

ref https://github.com/symfony/polyfill/pull/87

Commits
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7c33a013 Use PHP 7.2 polyfill instead of xml one

FriendsOfPHP/PHP-CS-Fixer,keradus/PHP-CS-Fixer,gharlan/PHP-CS-Fixer,kubawerlos/PHP-CS-Fixer,Slamdunk/PHP-CS-Fixer,FriendsOfPHP/PHP-CS-Fixer,Soullivaneuh/PHP-CS-Fixer,lucasmichot/PHP-CS-Fixer,Slamdunk/PHP-CS-Fixer,SpacePossum/PHP-CS-Fixer,lucasmichot/PHP-CS-Fixer,kubawerlos/PHP-CS-Fixer,GrahamCampbell/PHP-CS-Fixer,GrahamCampbell/PHP-CS-Fixer,gharlan/PHP-CS-Fixer,Soullivaneuh/PHP-CS-Fixer,keradus/PHP-CS-Fixer,SpacePossum/PHP-CS-Fixer