Abstract DDoc output for better document generation

[Tolga Cakiroglu via Digitalmars-d]

>
> Also see https://github.com/rejectedsoftware/ddox for DDOC 
> compatible documentation generator that uses the JSON output. 
> However, due to various shortcomings, of which not all are easy 
> to resolve, I'm planning to instead directly use a D parser at 
> some point.

Yes, this seems like a good tool. Actually, the reason o my 
thought was to take as much meta data from codes as possible to 
generate much more useful information. Not for documentation 
only, and analysis as well. This would remove the burden of 
defining and updating document generator on DMD, and move it to 
external tools.