Make dub part of the standard dmd distribution

[Atila Neves via Digitalmars-d]

> I'm fairly certain the ONLY real thing still preventing all 
> that above from actually working is that dub currently provides 
> no (practical) way to retrieve the necessary compiler/linker 
> args in order to actually use your dependencies (again, try 
> using vibe.d in, say, an rdmd-based project). I say no 
> "practical" way here because "dub describe -> parse the JSON -> 
> extract the needed info -> convert the needed info to compiler 
> flags" is NOT exactly practical or reasonable to expect people 
> to do *just* to use RDMD or otherwise opt-out of dub's 
> build-system.)

My build system already uses the output from `dub describe` to 
produce, well, a build system from it. I designed it with 
multiple backends in mind, right now the ones that I implemented 
are ninja and make.

If not for `dub describe` bugs (I'm working on that), you'd be 
able to point it at any dub project and get make/ninja files for 
it. Or integrate whatever you want with the existing files to 
compile that dub already knows about.

In fact, for any dub project that doesn't use configurations 
(that's the bug), you can do that _right now_.

Atila