Merge branch '4.0'

* 4.0:
  Updated HttpKernel component diagrams
  fix code block syntax
  Change value for opcache.memory_consumption
  Added a note about the dangers of dumping $_SERVER and $_ENV
  Updated the Guard diagram to add the new supports() method
  Fixed a missing reference
  Improved a routing example to show annotations
  Documented how to parse and dump custom YAML tags
  Clearer wording of allow_delete template behavior

Author: javiereguiluz