Add types from mirage/mirage-types directly in this repo
Add a mirage-types.lwt subpackage
Integrate the `mirage-types` code into `types`.

This is built as a separate library from the command-line tool, via the
`install-types` Makefile target.
Make the device initialization a generic Failure for now

This avoids exposing a concrete exception value in Mirage-types
Use the mirage-types.lwt packages in generated Makefiles
adapt Makefile for new build scheme (with unified mirage-types)
Fix two examples to open the V1_LWT module types so they compile