setup SSE
multiboot: convert info pointers from 32 to 64 bit
boot: point fs to TLS
lang: fix infinite recursion in __morestack
execute 64-bit Rust code
boot: remove 1 GB page requirement

Some virtual machines don't support this. Instead, populate a page directory
manually.
Makefile: enable debug info for assembly code
Makefile: add bochs target

Also uses cdrom for kvm because it can't directly load elf64 kernels.