DIP22 : Private symbol visibility

[Dicebot]

OK, I have finally got to it and separated proposal into 
http://wiki.dlang.org/DIP22 (private) and 
http://wiki.dlang.org/DIP22.1 (internal linkage). "Private" 
proposal is updated according to this discussion. "Internal 
linkage" proposal is only separated, with no real changes, 
because I am not sure how it is best to address them now.

Also I am going to be very busy for 2 months or so and if someone 
wants to volunteer to take this over and push into approval in 
any shape - I would have been very grateful.