Add := digraph to D

[Michel Colman]

> I believe that auto has been redefined in C++11 as well. In 
> both, all it really
> means is that the type is inferred.

That's what I seemed to remember as well. Originally it had 
something to do with scope, but it was basically obsolete because 
that was the default storage class anyway, so nobody was using it.

In the latest iteration of C++ they decided to redefine the 
keyword to mean automatic type inference. This avoided having to 
introduce a new keyword (which could break existing code that 
happened to use that word for a variable name) and it was 
unlikely to cause problems with old code. Storage class for local 
variables is still the same default anyway.

(The only possible error could be if someone wrote "auto a = b" 
as shorthand for "auto int a = b" with b some type other than 
int, which would have been legal in very old versions of C but 
extremely unlikely to ever be used since auto does nothing for an 
int)