[Dev] DMD D compiler contains non-free code

[Luke Shumaker]

The DMD D-language compiler's backend appears to be source-available,
but nonfree[0].

I believe this is somewhat widely known, but DMD doesn't appear on the
LibrePlanet wiki's list[1], and it is included in Parabola.

It seems at first glance that removing it may be tricky; the standard
library and runtime library want to be built in the same tree as it
(from my initial glance at the build scripts).  I'll look into it more
and get it out of Parabola when I get home.

[0]: https://raw.githubusercontent.com/D-Programming-Language/dmd/master/src/backendlicense.txt
[1]: https://libreplanet.org/wiki/List_of_software_that_does_not_respect_the_Free_System_Distribution_Guidelines

-- 
Happy hacking,
~ Luke Shumaker