This change:
* Makes the InclusionNode cache-safe by removing render-time side effects
to its nodelist.
* Ensures the render_context stack is properly scoped and reset by updating
the render call to use Template.render rather than Nodelist.render.
Specifically in rendering shortcuts, template responses, and class-based
views that return template responses.
Also added a test for render_to_response(status=...) which was missing
from fdbfc980.
Thanks Tim and Carl for the review.
Merged BaseIncludeNode, ConstantIncludeNode and Include node.
This avoids raising TemplateDoesNotExist at parsing time, allows recursion
when passing a literal template name, and should make TEMPLATE_DEBUG behavior
consistant.
Thanks loic84 for help with the tests.
Fixed#3544, fixed#12064, fixed#16147
