Putting a toc in the sidebar used to work, but was broken by
commit 9652cdfe2eb16150518e34af33c8858118fe0a09, which, in turn fixed a bug
with the toc not appearing during page preview.

So, if toc is a sanitize hook, it can't be used in the sidebar, because the
sidebar is only added to the page later. If the toc is a format hook, it
shows up in the sidebar, but not at page preview time (because format hooks
are not called during preview). Also, calling the toc as a format hook
makes any headers that are hardcoded into the page template show up in the
toc, which is rarely desirable.

I can't think of a way between these that works in all cases. Maybe call
the format hooks when generating a page preview? Maybe add an option to toc
to make it embeddable in the sidebar? 

Hmm, I think I need to call format during preview. Another case is that
inline uses a format hook to insert the inlined content..

--[[Joey]]

[[done]]
