destpage does not normally need to be worried about when creating other files
as part of the process of rendering a page. Using destpage results in
inlined pages creating two copies of such files. It works to not use destpage
in this case because the inlining page depends on the source page, so if the
source page is modified or deleted the inlining page will be updated.
set to the destination page. This avoids need for hacks to munge the urls
in preview mode, which fixes several bugs.
* Several destpage fixes in plugins.