- Don't wildcard-import from arch modules. Make it explicit.
- Put translation table code into its own module.
- Put boot code in boot.rs instead of cpu.rs
- Other minor changes, most memory subsystem.
register-rs 1.0.0 now uses UnsafeCell internally, which means we lost the Copy
derive on InMemoryRegister.
Therefore, a small set of changes was needed in the MMU driver to dance around
the static array init depending on a Copy type.