[ocaml-platform] Changes to my previous proposal for namespaces

[Leo White]

> This is one thing I don't quite understand.  Yes, modules are implemented as records at runtime, but there's no
> requirement that namespaces have any runtime representation; I don't see why they can't exist at compile time only as
> something to make changes to the compilation environment when invoked
> (open or # or whatever).

Namespaces will indeed only exist at compile-time.

> As far as the open/
> closed distinction, hasn't gasche has gone over this; they can be treated as closed by the compiler during compilation
> even if they're open all the rest of the time. 

Ensuring a well-defined ordering between multiple "automatically opened
modules" would require namespaces to be closed all the time, not just
during a particular compilation.