Fix delete! usage so that BinDeps works on all v0.2-pre versions of julia

BinDeps will break after https://github.com/JuliaLang/julia/commit/e421dc3ea7fab020d5c87fcddabfe619bebf7c3e without this change, so it would be good to apply and update METADATA asap.  It will still work with older versions with this change.