Revamping associative arrays

[Walter Bright]

language_fan wrote:
> It would be great if the underlying implementation could be switched 
> based on the task at hand. The AAs could be completely library provided, 
> with only a small built-in syntactical sugaring on top of it.

They already are. In D1, the complete implementation is in 
phobos/internal/aaA.d, and the compiler knows nothing about it other 
than the function signatures.