Change to fix build error in ioreg

Addition of where clause to Rust.
Change to fix build error in ioreg

Addition of where clause to Rust.
Renamed Vector -> Slice
Added where_clause to other missing places
Merge pull request #138 from farcaller/fix-nightly

Fixes for nightly fallout

Reviewed-by: farcaller
Merge branch 'master' of https://github.com/hackndev/zinc
ioreg/parser: Nightly fallout
platformtree: Prefer indexing to _.get()
ioreg::setter: Make documentation consistent with others
ioreg::parser: Rework doc comments

Add support for inner and trailing doc comments.
k20::{sim, pin}: Port to ioregs!
k20::uart: Port to ioregs!