Redox unix 0.13.5 rebased to ring head
This fixes problems reported here: redox#1342 (closed)
Tested OK with x86_64-unknown-redox and manual edits to various Cargo.toml files that relied on ring.
Ideally this should be force pushed as a branch with the same redox-unix-0.13.5 name so everything dependent on this works without mods.