Druntime AA interface could be enhanced a bit

[Walter Bright]

BLS wrote:
> I guess what I want to ask is
> Are D AAs really so fundamental ?

Yes, I believe they are. For one thing, they are highly useful in CTFE, which 
would be difficult to do if they were a user defined type.

> Are D AAs flexible enough ?

Yes, the criticisms of them tend to be about their performance, not suitability 
for a wide variety of applications.