Merge branch '4.4' into 5.0

* 4.4:
  [PropertyInfo] Update property_info.rst

Author: javiereguiluz

components/property_info.rst

@@ -487,6 +487,12 @@ service by defining it as a service with one or more of the following
 * ``property_info.type_extractor`` if it provides type information.
 * ``property_info.description_extractor`` if it provides description information.
 * ``property_info.access_extractor`` if it provides access information.
+* ``property_info.initializable_extractor`` if it provides initializable information
+  (it checks if a property can be initialized through the constructor).
+
+.. versionadded:: 4.2
+
+    The ``property_info.initializable_extractor`` was introduced in Symfony 4.2.
 
 .. _`phpDocumentor Reflection`: https://github.com/phpDocumentor/ReflectionDocBlock
 .. _`phpdocumentor/reflection-docblock`: https://packagist.org/packages/phpdocumentor/reflection-docblock