Add initial i686 arch module

src/arch/mod.rs

src/arch/x86/consts.rs

src/arch/x86/cpuid.rs

src/arch/x86/debug.rs

src/arch/x86/device/cpu.rs

src/arch/x86/device/hpet.rs

src/arch/x86/device/ioapic.rs

src/arch/x86/device/local_apic.rs

src/arch/x86/device/mod.rs

src/arch/x86/device/pic.rs

src/arch/x86/device/pit.rs

src/arch/x86/device/rtc.rs

src/arch/x86/device/serial.rs

src/arch/x86/device/system76_ec.rs

src/arch/x86/gdt.rs

src/arch/x86/idt.rs

src/arch/x86/interrupt/exception.rs

src/arch/x86/interrupt/handler.rs

src/arch/x86/interrupt/ipi.rs

src/arch/x86/interrupt/irq.rs