Associative arrays

[TheFlyingFiddle via Digitalmars-d-learn]

I have a few questions about the pseudo built in associative 
arrays.

1. Is it possible to have the built in associative array use a 
custom allocator from std.experimental.allocator to service it's 
allocation needs?

2. A while ago I read on the newsgroup a while back that there 
was a plan to make it possible for a user to swap out the 
standard associative array implementation by modifying druntime 
and or implementing some linker functions. Have this been done 
yet? And if so what must I do to swap the implementation?