Add D front-end, libphobos library, and D2 testsuite... to GCC

[Walter Bright]

On 10/28/2018 8:43 PM, Mike Parker wrote:
> Congratulations are in order for Iain Buclaw. His efforts have been rewarded in 
> a big way. Last Friday, he got the greenlight to move forward with submitting 
> his changes into GCC:

Reddit: 
https://www.reddit.com/r/programming/comments/9sb74k/the_d_language_frontend_finally_merged_into_gcc_9/

HackerNews (at #12 on the front page):
https://news.ycombinator.com/news