Merge branch '2018' into 'master'

Cargo.toml

src/allocator/linked_list.rs

src/allocator/mod.rs

src/arch/x86_64/debug.rs

src/arch/x86_64/device/local_apic.rs

src/arch/x86_64/device/mod.rs

src/arch/x86_64/device/pic.rs

src/arch/x86_64/device/pit.rs

src/arch/x86_64/device/rtc.rs

src/arch/x86_64/device/serial.rs

src/arch/x86_64/gdt.rs

src/arch/x86_64/idt.rs

src/arch/x86_64/interrupt/exception.rs

src/arch/x86_64/interrupt/ipi.rs

src/arch/x86_64/interrupt/irq.rs

src/arch/x86_64/interrupt/syscall.rs

src/arch/x86_64/interrupt/trace.rs

src/arch/x86_64/paging/entry.rs

src/arch/x86_64/paging/mapper.rs

src/arch/x86_64/paging/mod.rs