Fixed #11889: Documented the fact that context processors will overwrite...

name, the second will override the first. The default processors are explained

below.

.. 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.

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

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

``RequestContext`` instance gets a ``ip_address`` variable::