Module system of D2: to be fixed still

[bearophile]

The current module&package system of D2 needs to be fixed, it has some conceptual/semantic/logic holes. It looks like the result a good design stopped mid-way.

I have discussed them three times in the past, and now that Phobos2 is mostly here and only a better support for multi-threading programming is planned to be added to D2, it's a good moment to list all the troubles with the module&package system, and to fix the current half-backed and partially broken/illogical situation.
I'll remind this few months from now again if in the meantime things have not improved yet.

Thank you,
bearophile