Last SQLite-Net Extensions version works with SQLite.Net-PCL out-of-the-box and the PCL library project is now compiled against SQLite.Net-PCL NuGet Package. Default profile is Profile158 (.Net 4.5, SL5, WP8, Win8, Xam.Droid & Xam.Touch).
EDIT: The library is now available as a NuGet package. So it should be simpler to include it.