Merge branch 'update_toolchain' into 'master'

Cargo.lock

Cargo.toml

Makefile

core_io

rust-toolchain

src/crti/src/lib.rs

src/crtn/src/lib.rs

src/header/setjmp/impl/x86_64/longjmp.s

src/header/setjmp/impl/x86_64/setjmp.s

src/header/signal/linux.rs

src/header/signal/redox.rs

src/header/unistd/mod.rs

src/header/wchar/utf8.rs

src/lib.rs