Add libdrm wrap file
Created by: ascent12
Closes #35 (closed)
This pulls in libdrm to get the latest Linux userspace API headers, but does not actually build or link against the libdrm subproject.
This allows us to remove compat.h, as we can assume we always have the latest headers.
The "just use the headers" case works, which I've tested on Debian stable. It possibly requires one extra step by the users, which is just as annoying as if this was done as a git submodule.
Currently using libdrm as a proper subproject (like json-c is) will fail, which is fixed by mesa/drm!37 (merged) I'm not sure if it's worth delaying this PR for this, though.