Merge branch '4.4' into 5.0

* 4.4:
  add use statement
  Add Blackfire Docker support for the local web server

Author: OskarStark

components/mailer.rst

@@ -61,6 +61,7 @@ it:
 Then, use the SMTP Gmail transport::
 
     use Symfony\Component\Mailer\Bridge\Google\Smtp\GmailTransport;
+    use Symfony\Component\Mailer\Mailer;
 
     $transport = new GmailTransport('user', 'pass');
     $mailer = new Mailer($transport);

setup/symfony_server.rst

@@ -304,7 +304,8 @@ Elasticsearch 9200      ``ELASTICSEARCH_``
 MongoDB       27017     ``MONGODB_`` (set the database via a Docker ``MONGO_DATABASE`` env var)
 Kafka         9092      ``KAFKA_``
 Mailcatcher   1025/1080 ``MAILER_``
-              25/80
+              or 25/80
+Blackfire     8707      ``BLACKFIRE_``
 ============= ========= ======================
 
 You can open web management interfaces for the services that expose them: