Merge branch '3.2' into 3.3

* 3.2:
  Fix optional cache warmers are always instantiated whereas they should be lazy-loaded
  add some \ on PHP_VERSION_ID for 2.8
  [PropertyInfo][DoctrineBridge] The bigint Doctrine's type must be converted to string

Author: nicolas-grekas

CompiledRoute.php

@@ -73,7 +73,7 @@ public function serialize()
      */
     public function unserialize($serialized)
     {
-        if (PHP_VERSION_ID >= 70000) {
+        if (\PHP_VERSION_ID >= 70000) {
             $data = unserialize($serialized, array('allowed_classes' => false));
         } else {
             $data = unserialize($serialized);

Route.php

@@ -116,7 +116,7 @@ public function serialize()
      */
     public function unserialize($serialized)
     {
-        if (PHP_VERSION_ID >= 70000) {
+        if (\PHP_VERSION_ID >= 70000) {
             $data = unserialize($serialized, array('allowed_classes' => array(CompiledRoute::class)));
         } else {
             $data = unserialize($serialized);