Fix Clippy warnings

src/header/netdb/host.rs

src/header/netdb/lookup.rs

src/header/netdb/mod.rs

src/header/pwd/mod.rs

src/header/stdio/constants.rs

src/header/stdio/mod.rs

src/header/stdio/printf.rs

src/header/stdio/scanf.rs

src/header/stdlib/mod.rs

src/header/stdlib/sort.rs

src/header/sys_select/mod.rs

src/header/unistd/mod.rs

src/header/wchar/mod.rs

src/ld_so/linker.rs

src/ld_so/start.rs

src/ld_so/tcb.rs

src/lib.rs

src/platform/pte.rs

src/platform/rlb.rs

src/start.rs