Fix #2529: explicit protection package #3651

[Kagamin via Digitalmars-d-announce]

On Wednesday, 20 August 2014 at 07:47:36 UTC, ketmar via 
Digitalmars-d-announce wrote:
> but it requires to dump all 'subpackages' into one flat 
> directory and
> with ugly names.

Huh? If std.datetime and std.regex are subpackages of `std` 
package, it usually means, they should reside in `std` directory, 
no? And how explicit package protection can change that?