Merge remote-tracking branch 'origin/truncate-n-mkfifo'

src/header/unistd/mod.rs

src/platform/linux/mod.rs

src/platform/redox/mod.rs

tests/Makefile

tests/expected/futimens.stderr

tests/expected/futimens.stdout

tests/expected/mkfifo.stderr

tests/expected/mkfifo.stdout

tests/futimens.c

tests/mkfifo.c

tests/unistd/ftruncate.c