Corrected File, ContentFile, and ImageFile signatures in docs.

docs/ref/files/file.txt

@@ -10,7 +10,7 @@ for basic file handling in Django.
 The ``File`` class
 ==================
 
-.. class:: File(file_object)
+.. class:: File(file_object, name=None)
 
     The :class:`File` class is a thin wrapper around a Python
     :py:term:`file object` with some Django-specific additions.
@@ -91,7 +91,7 @@ The ``File`` class
 The ``ContentFile`` class
 =========================
 
-.. class:: ContentFile(File)
+.. class:: ContentFile(content, name=None)
 
     The ``ContentFile`` class inherits from :class:`~django.core.files.File`,
     but unlike :class:`~django.core.files.File` it operates on string content
@@ -107,7 +107,7 @@ The ``ContentFile`` class
 The ``ImageFile`` class
 =======================
 
-.. class:: ImageFile(file_object)
+.. class:: ImageFile(file_object, name=None)
 
     Django provides a built-in class specifically for images.
     :class:`django.core.files.images.ImageFile` inherits all the attributes