SDL 2.0.6 was just released , so I've updated DerelictSDL2 
to support it. It's available in DerelictSDL2 3.1.0-alpha.1. I've
tested that the loader works, but beyond that I've done nothing
I also fixed some minor issues in the 3.0 branch, the latest
release of which is 3.0.0-beta.7.
The 3.0 series supports SDL 2.0.0 - SDL 2.0.5, and the 3.1 series
supports SDL 2.0.0 - 2.0.6. The latter is currently not in the
master branch (it's in the 3.1 branch), nor is it in the
documentation. I'll move 3.1 development to master and update the
docs once I pull it out of alpha.