Adding D Editor Support

[Walter Bright]

John A. De Goes wrote:
> Without documentation on the format, the best I can do is to
> experiment with the compiler and try to elicit all possible
> errors/warnings. And hope they fall into a small number of consistent
> patterns (which seems likely given that all the errors I encountered
> so far matched the above patterns).
> 
> Anyone having inside knowledge of the format care to save me some
> time here? (Walter, you listening? :-)

No problem. dmd.zip comes with compiler source, just grep for calls to 
the function "error(". No need to experiment!