Cleanup Redox repo, update Rust, remove old target

Cargo.toml

arch/arm/Cargo.toml

arch/arm/src/context.rs

arch/arm/src/externs.rs

arch/arm/src/interrupt.rs

arch/arm/src/lib.rs

arch/arm/src/linker.ld

arch/arm/src/panic.rs

arch/arm/src/start.rs

arch/test/Cargo.toml

arch/test/src/interrupt.rs

arch/test/src/lib.rs

arch/test/src/main.rs

arch/test/src/time.rs

arch/x86_64/Cargo.toml

arch/x86_64/src/acpi/dmar/drhd.rs

arch/x86_64/src/acpi/dmar/mod.rs

arch/x86_64/src/acpi/fadt.rs

arch/x86_64/src/acpi/madt.rs

arch/x86_64/src/acpi/mod.rs