Make relibc (except libm) pure Rust

.gitlab-ci.yml

Cargo.lock

Cargo.toml

Makefile

build.rs

include/bits/fcntl.h

include/bits/stdio.h

include/bits/stdlib.h

include/bits/sys/ptrace.h

include/bits/unistd.h

src/c/fcntl.c

src/c/ptrace.c

src/c/stack_chk.c

src/c/stdio.c

src/c/stdlib.c

src/c/unistd.c

src/c/wchar.c

src/header/fcntl/mod.rs

src/header/pty/linux.rs

src/header/pty/redox.rs