[[!tag wishlist]]

It would be nice to have pagespecs support "link(.)" as syntax.
This would match pages that link to the page that invokes the pagespec.
The use case is a blog with tags, and having a page for each tag
which uses !inline to list all posts with the tag.

Joey said on IRC that "probably changing the derel() function in 
IkiWiki.pm is the best way to do it".

