[rust-dev] Renaming of core and std

Hi everyone, There's been consensus lately that `core` and `std` are somewhat misnamed. `core` is really the standard library--the one that would be specified in a specification if we had one. `std` is an "extras" library and may well end up sliced up and moved to various packages. So it seems prudent to rename `core` to `std`. But that leaves the question of what to name `std` in the interim. Options that have been suggested are `extra`, `ext`, and `contrib`. Any other opinions? Patrick