Merge branch 'core-io' into 'master'

include/bits/stdio.h

src/fs.rs

src/header/stdio/constants.rs

src/header/stdio/default.rs

src/header/stdio/helpers.rs

src/header/stdio/internal.rs

src/header/stdio/mod.rs

src/header/stdio/scanf.rs

src/platform/linux/mod.rs

src/platform/mod.rs

src/platform/pal/mod.rs

src/platform/redox/mod.rs

tests/Makefile

tests/expected/stdio/buffer.stderr

tests/expected/stdio/buffer.stdout

tests/expected/stdio/fgets.stderr

tests/expected/stdio/fgets.stdout

tests/expected/stdio/fseek.stderr

tests/expected/stdio/fseek.stdout

tests/expected/stdio/setvbuf.stdout