[2.2.x] Removed extra characters in docs header underlines.

Backport of 25829197bb from master

docs/howto/custom-model-fields.txt

@@ -692,7 +692,7 @@ existing conversion code::
             return self.get_prep_value(value)
 
 Some general advice
---------------------
+-------------------
 
 Writing a custom field can be a tricky process, particularly if you're doing
 complex conversions between your Python types and your database and
@@ -731,7 +731,7 @@ told to use it. To do so, simply assign the new ``File`` subclass to the special
 ``attr_class`` attribute of the ``FileField`` subclass.
 
 A few suggestions
-------------------
+-----------------
 
 In addition to the above details, there are a few guidelines which can greatly
 improve the efficiency and readability of the field's code.

docs/intro/tutorial03.txt

@@ -413,7 +413,7 @@ template (or templates) you would change it in ``polls/urls.py``::
     ...
 
 Namespacing URL names
-======================
+=====================
 
 The tutorial project has just one app, ``polls``. In real Django projects,
 there might be five, ten, twenty apps or more. How does Django differentiate

docs/ref/databases.txt

@@ -839,7 +839,7 @@ Example of a full DSN string::
     ),
 
 Threaded option
-----------------
+---------------
 
 If you plan to run Django in a multithreaded environment (e.g. Apache using the
 default MPM module on any modern operating system), then you **must** set

docs/releases/1.0-porting-guide.txt

@@ -298,7 +298,7 @@ Old (0.96)            New (1.0)
 ===================== =====================
 
 Work with file fields using the new API
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 The internal implementation of :class:`django.db.models.FileField` have changed.
 A visible result of this is that the way you access special attributes (URL,
@@ -644,7 +644,7 @@ Testing
 -------
 
 :meth:`django.test.Client.login` has changed
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Old (0.96)::
 

docs/releases/1.1.txt

@@ -267,7 +267,7 @@ A few notable improvements have been made to the :doc:`testing framework
 </topics/testing/index>`.
 
 Test performance improvements
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 .. currentmodule:: django.test
 

docs/topics/auth/passwords.txt

@@ -547,7 +547,7 @@ Django includes four validators:
     Validates whether the password is not entirely numeric.
 
 Integrating validation
------------------------
+----------------------
 
 There are a few functions in ``django.contrib.auth.password_validation`` that
 you can call from your own forms or other code to integrate password

docs/topics/pagination.txt

@@ -77,7 +77,7 @@ page::
 .. _using-paginator-in-view:
 
 Using ``Paginator`` in a view
-==============================
+=============================
 
 Here's a slightly more complex example using :class:`Paginator` in a view to
 paginate a queryset. We give both the view and the accompanying template to