Testing with nearly all packages in code.dlang.org

[Atila Neves]

In the spirit of avoiding any further breakage, I wrote a little 
D script to get a list of all dub packages that still build since 
projects get stale. It took ~44min on my laptop using 20 threads 
to try and build all 2381 (as of yesterday) dub packages. This 
included downloading all of them, I did an `rm -rf 
~/.dub/packages` just before.

1362 of them returned 0 for `dub build`, or about 57%. It's 
probably a good idea to actually do `dub build --build=unittest` 
since that'll include more D code.

I don't know if some of them fail because they need custom 
build/CI; I think it's safe to ignore them even if that's the 
case, since a dub package needs to just build with dub.

The list and the code is at 
https://github.com/atilaneves/all-dub-packages.