Vim syntax file types and traits cleanup
auto merge of #15292 : alxgnon/rust/vim_syntax_cleanup, r=cmr

- Fix a couple mistakes:
  - `Ordering` is an enum, not a trait.
  - `Container` is now named `Collection`.
  - Add missing `CheckedDiv`.
  - Remove obsolete `OwnedVector`.
- Reorganize some lines to match [prelude's arrangement](http://doc.rust-lang.org/std/prelude/#reexports), making mistakes easier to spot in the future.