[development] Core drupal.module moved to contribsite_network.module

[Daniel F. Kudwien]

> Actually, I'm not even sure what would happen to @drupal.org accounts on g.d.o 
> or blogs if drupal.org just switched off drupal.module.  Would they still be 
> accessible somehow?

That was one of my first thoughts either. I first thought, most the sites running drupal.module are experimental / for demonstration purposes. However, g.d.o is an example for a rather big site using it.

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