To handle this, avoid populating %renderedfiles in preview,
and in expiry, check if the file is in %renderedfiles, if it is
do not delete it since it was saved.
Conflicts:
IkiWiki/Plugin/recentchanges.pm
Note that smcv's approach of using urlto also gets the url right when
redirecting to a non-html file, which is a better approach than my recent
fix to recentchanges
Joey Hess
Simon McVittie