Organize files to make building for multiple archs easier

Makefile

asm/aarch64/dummy.S

asm/arm/start.s

asm/x86-unknown-none/bootloader.asm

asm/x86-unknown-none/descriptor_flags.inc

asm/x86-unknown-none/gdt_entry.inc

asm/x86-unknown-none/memory_map.asm

asm/x86-unknown-none/old/cpuid.asm

asm/x86-unknown-none/old/cpuid.inc

asm/x86-unknown-none/old/initialize.asm

asm/x86-unknown-none/old/vesa.asm

asm/x86-unknown-none/old/vesa.inc

asm/x86-unknown-none/print.asm

asm/x86-unknown-none/stage1.asm

asm/x86-unknown-none/stage2.asm

asm/x86-unknown-none/thunk.asm

asm/x86-unknown-none/unreal.asm

linkers/x86-unknown-none.ld