Precompiled filters

Add support for precompiled filters
Yep, I implemented `setcdr` in a later commit when I realized that `setf` wouldn't work with 24.2 and below. I'm just hesitant to bring reliance on another package unless it's truly beneficial (as it would be with the filter function). I don't know all of what `cl-lib` can offer, so this is a case of "I know what I don't know".