[1.5.x] Fixed #22167 -- Improved documentation on context processors

.. admonition:: When context processors are applied

    When you use ``RequestContext``, the variables you supply directly

    are added first, followed any variables supplied by context

    processors. This means that a context processor may overwrite a

    variable you've supplied, so take care to avoid variable names

    which overlap with those supplied by your context processors.

    Context processors are applied *after* the context itself is processed.

    This means that a context processor may overwrite variables you've

    supplied to your ``Context`` or ``RequestContext``, so take care

    to avoid variable names that overlap with those supplied by your

    context processors.

Also, you can give ``RequestContext`` a list of additional processors, using the

optional, third positional argument, ``processors``. In this example, the

    the same as a call to :func:`~django.shortcuts.render_to_response()` with a

    context_instance argument that forces the use of a ``RequestContext``.

    Note that the contents of a supplied dictionary (``my_data_dictionary``

    in this example) will take precedence over any variables supplied by

    context processors or the ``RequestContext``.

Here's what each of the default processors does:

django.contrib.auth.context_processors.auth