[#10461] Add docs about custom environment
fixed CS
Fixed bug that incorrectly causes the "required" attribute to be omitted from select even though it contains the "multiple" attribute
fixed comment in forms.xml file
Fix #8205 : Deprecate file mode update when calling dumpFile
Merge branch '2.3' into 2.4

* 2.3: (34 commits)
  Fix #8205 : Deprecate file mode update when calling dumpFile
  Fix #10437: Catch exceptions when reloading a no-cache request
  Fix libxml_use_internal_errors and libxml_disable_entity_loader usage
  removed ini check to make uploadedfile work on gae
  Update OptionsResolver.php
  fixed comment in forms.xml file
  Clean KernelInterface docblocks
  Cast the group name as a string
  Fixed doc of InitAclCommand
  [Form] Fix "Array was modified outside object" in ResizeFormListener.
  Fix IBAN validator
  [Process] Remove unreachable code + avoid skipping tests in sigchild environment
  Fixed bug that incorrectly causes the "required" attribute to be omitted from select even though it contains the "multiple" attribute
  Added travis_retry to .travis.yml
  [Process] fix some typos and refactor some code
  [Process] Fix unit tests in sigchild disabled environment
  [Process] Trow exceptions in case a Process method is supposed to be called after termination
  fixed typo
  [Process] fixed fatal errors in getOutput and getErrorOutput when process was not started
  [Process] Fix escaping on Windows
  ...

Conflicts:
	src/Symfony/Component/DomCrawler/Crawler.php
	src/Symfony/Component/Filesystem/Filesystem.php
	src/Symfony/Component/Process/Process.php