Make dub part of the standard dmd distribution

[Atila Neves via Digitalmars-d]

> rdmd could collect dependencies while performing the actual 
> compilation. Then, if the dependencies are stable (compare with 
> the saved ones), all done in one run. Otherwise, discard the 
> output and rebuild.

I wrote a silly tool that gathers dependencies as it compiles. 
Essentially, it calls dmd -v and parses the result as rdmd does. 
The net effect is something akin to gcc's -MF -MD combo.

It's part of the build system I keep pestering everyone about. I 
had to write it because Ninja depends on it for proper dependency 
tracking. Make needs it too, but the Makefile code I have to 
generate is best not looked at. Make's fault, not mine.

Atila