[Yaml] mark some classes as final

Author: xabbuh

CHANGELOG.md

@@ -4,6 +4,8 @@ CHANGELOG
 3.4.0
 -----
 
+ * the `Dumper`, `Parser`, and `Yaml` classes are marked as final
+
  * Deprecated the `!php/object:` tag which will be replaced by the
    `!php/object` tag (without the colon) in 4.0.
 

Dumper.php

@@ -15,6 +15,8 @@
  * Dumper dumps PHP variables to YAML strings.
  *
  * @author Fabien Potencier <[email protected]>
+ *
+ * @final since version 3.4
  */
 class Dumper
 {

Parser.php

@@ -18,6 +18,8 @@
  * Parser parses YAML strings to convert them to PHP arrays.
  *
  * @author Fabien Potencier <[email protected]>
+ *
+ * @final since version 3.4
  */
 class Parser
 {

Yaml.php

@@ -17,6 +17,8 @@
  * Yaml offers convenience methods to load and dump YAML.
  *
  * @author Fabien Potencier <[email protected]>
+ *
+ * @final since version 3.4
  */
 class Yaml
 {