It's probably better to wait until the buffer is sent, rather than
waiting until its empty. To test the output it has to be sent, but
because of timing, it may be emptied at any point.
- reordered includes to prevent accidental dependencies.
- moved arch specific files into their own folder (easier to include with cmake).
- renamed non-class files to reflect new code style (lower case with underscores).
- using full relative paths for includes (easier for understanding dependencies).
- using #pragma once instead of classic-style header guards.
