Merge branch '3.4' into 4.0

* 3.4:
  Updated HttpKernel component diagrams
  fix code block syntax
  Change value for opcache.memory_consumption
  Updated the Guard diagram to add the new supports() method
  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