[dmd-internals] AssociativeArray in druntime should go before the next release

[Martin Nowak]

>> I _suspect_ that if we try this, we'll find it isn't yet possible to
>> do library AAs. Are we able to generate error messages at compile time
>> when the same key is used twice? Maybe, maybe not. For sure we'll have
>> to deal with template bloat.
No template bloat needed if the implementation would use an untyped  
implementation
with comparison/hash callbacks. But this making them templated might be a  
performance win.