Use the `BTree*` variants ...
Use the `BTree*` variants ...

rust-lang-nursery/rustc-serialize,ajroetker/rustc-serialize,rust-lang-deprecated/rustc-serialize,indefini/rustc-serialize,SimonSapin/rustc-serialize,shepmaster/rustc-serialize,rust-lang/rustc-serialize,DenisKolodin/rustc-serialize,gbersac/rustc-serialize