Proof of concept - library AA

[Martin Nowak via Digitalmars-d]

On Sunday, 24 May 2015 at 14:13:26 UTC, Martin Nowak wrote:
> Would be interesting to get some opinions on this.
>
> https://github.com/D-Programming-Language/druntime/pull/1282

Bringing up this topic again b/c there was still almost no 
feedback on the actual plan. Here is a summary.

- built-in AA is too magic to be replaced by library AA
- provide a general purpose library AA with enough benefits for 
people to live with incompatibilities
- add a cheap toBuiltinAA adapter for compatibility of the 
library AA with existing code
- make array and AA literals usable with UDTs
- slowly deprecated magic behavior of the built-in AA
- switch built-in AA to library AA

Also we should plan for a std.container.aa to deal w/ all the 
fancy generic/specialized stuff.