[gsoc] D Language Server protocol based on the DMD frontend

[rikki cattermole]

These two bugs can be considered blockers (Win64):

https://issues.dlang.org/show_bug.cgi?id=18810
https://issues.dlang.org/show_bug.cgi?id=18811

The first shouldn't be too much work for a hacky solution. Port file to 
D, version as required and move to root/.
The second I haven't retested with the precise GC. It may solve it. 
Otherwise I have got no idea where to go from here.