Used to work, then the default join from `fdroid_app` to `fdroid_apk`
was removed for performance reasons. This adds the join back, but requires
queries to explicitly opt in to the join if they require it. The specific
query for known vulns is not a performance problem, because sqlite is able
to narrow the result set quite substantially before requiring a join onto the
fdroid_apk table anyway (e.g. by using the "installed app" table).
2bd70fc6b5