Squashed 'src/machinetalk/proto/' changes from def19ec..f24e102

f24e102 machinetalk-protobuf: added types for EMC error channel

git-subtree-dir: src/machinetalk/proto
git-subtree-split: f24e1021900ac7ca97d0042aeb239a9ff0a8130e
Merge commit '9d50507a1acf9a6d481e26d5fdf16dec278dcb1c' into machinetalk-preview-strahlex