Using a file was sorta not right.
Note that when previewing, %pagestate is not saved, so
it has to rebuild the graph every time until that graph is saved;
then previews can use the cached data until the next time the graph
is changed.
Also note that it's stored in the destpage's pagestate. The imagemap
could vary between a page and an inlined page if wikilinks were supported.
Also, I let preview mode write real files, rather than using data: uri.
Which is ok these days, since ikiwiki tracks files created during
previewing, and cleans them up later.
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.
for extended pagespecs. The old calling convention will still work for
back-compat for now.
* The calling convention for functions in the IkiWiki::PageSpec namespace
has changed so they are passed named parameters.
* Plugin interface version increased to 2.00 since I don't anticipate any
more interface changes before 2.0.