Merge branch '4.4' into 5.0

* 4.4: (26 commits)
  [HttpClient] NativeHttpClient should not send >1.1 protocol version
  [HttpClient] fix support for non-blocking resource streams
  [Mailer] Make sure you can pass custom headers to Mailgun
  [Mailer] Remove line breaks in email attachment content
  Update links to documentation
  [Validator] Add the missing translations for the Arabic (ar) locale
  ensure to expect no validation for the right reasons
  [Security-Guard] fixed 35203 missing name tag in param docblock
  [HttpClient] fix casting responses to PHP streams
  [PhpUnitBridge] Add test case for @expectedDeprecation annotation
  [PhpUnitBridge][SymfonyTestsListenerTrait] Remove $testsWithWarnings stack
  [Mailer] Fix addresses management in Sendgrid API payload
  [Mailer][MailchimpBridge] Fix missing attachments when sending via Mandrill API
  [Mailer][MailchimpBridge] Fix incorrect sender address when sender has name
  [HttpClient] fix capturing SSL certificates with NativeHttpClient
  Update year in license files
  [TwigBridge][Form] Added missing help messages in form themes
  Update year in license files
  Update year in license files
  fix version when "anonymous: lazy" was introduced
  ...

LICENSE

@@ -1,4 +1,4 @@
-Copyright (c) 2016-2019 Fabien Potencier
+Copyright (c) 2016-2020 Fabien Potencier
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal