Support queries like "incategory:Felis_silvestris_catus (intitle:Birds OR intitle:Dogs)" (Anything in the cat category that has either Birds or Dogs in the title)
Or more generally things like intitle:ogv OR intitle:ogg OR intitle:webm to do a pseudo search of only videos
(From merged task, also causes log-errors of the "Search backend error during full_text search" type)