stale after a session undo.

Switches to short-circuit rendering.
New expand, which needs to be tested.
Now check security of items, and new skip_unauthorized attr.
New branches_expr.

Added lock around parse_cookie.

Changed the way module info is managed to improve thread safety.

Changed to exclude error value from traceback when it was displayed
as a message.

attributes to fail.

compiled as a template but only the templates blocks are saved, and
later rendered directly with render_blocks.

Added with tag.

Also, for the HTML syntax, we now allow spaces after # and after end
or '/'.  So, the tags::

  <!--#
    with spam
    -->

and::

  <!--#
    end with
    -->

are valid.

attributes, causing an apparent role leak.

no longer exists)