Merge branch '2.7' into 2.8

* 2.7:
  Fix 7.2 compat layer
  Fix PHP 7.2 support
  [HttpFoundation] Add missing session.lazy_write config option
  [HttpFoundation] Combine Cache-Control headers
  [Form] fix parsing invalid floating point numbers
  Escape command usage when displaying it in the text descriptor
  Use for=ID on radio/checkbox label.

Author: nicolas-grekas

Tests/Fixtures/validresource.php

@@ -1,5 +1,8 @@
 <?php
 
+if (function_exists('__phpunit_run_isolated_test')) {
+    return;
+}
 /** @var $loader \Symfony\Component\Routing\Loader\PhpFileLoader */
 /** @var \Symfony\Component\Routing\RouteCollection $collection */
 $collection = $loader->import('validpattern.php');