Fix warnings

src/header/assert/mod.rs

src/header/bits_pthread/mod.rs

src/header/bits_sched/mod.rs

src/header/inttypes/mod.rs

src/header/locale/mod.rs

src/header/netdb/dns/mod.rs

src/header/pthread/mod.rs

src/header/pthread/mutex.rs

src/header/signal/mod.rs

src/header/stdio/mod.rs

src/header/stdio/scanf.rs

src/ld_so/mod.rs

src/platform/redox/clone.rs

src/platform/redox/exec.rs

src/platform/redox/extra.rs

src/platform/redox/mod.rs

src/platform/redox/path.rs

src/platform/redox/ptrace.rs

src/platform/redox/redox-exec/src/lib.rs

src/pthread/mod.rs