Splitting out UEFI bootloader code from kernel

Now the bootloader should be responsible for all initial setup,
loading the kernel, and then handing off to the kernel with
proper data in place.

src/arch/x86_64/config.mk

@@ -1,5 +1,5 @@
 AS := nasm
-ASFLAGS := -felf
+ASFLAGS := -felf64
 LDFLAGS := -m elf_x86_64
 CFLAGS := -march=nocona -m64