PointerList.Set(): refactor name from tgt to src to clarify; add comments to code to explain the version handling
PointerList.Set(): refactor name from tgt to src to clarify; add comments to code to explain the version handling

hodduc/go-capnproto2,zombiezen/go-capnproto2,zombiezen/go-capnproto,hodduc/go-capnproto2,zombiezen/go-capnproto,zombiezen/go-capnproto2,tpukep/caps