WIP: Reformat everything (testing only, don't merge)

$ scripts/clang-formatter.sh ./
Formatting directory: clang-format -i ./
Formatting finished. If the changes are a mistake you can call: 'git reset --hard'.
 422 files changed, 70801 insertions(+), 57992 deletions(-)

Locally I checked compilation before I made .clang-format compatibile with xenial and stretch. Let's see if this works.

I used

git config --local user.email clang-formatter
git config --local user.name "clang-formatter"
git commit --amend --author "clang-formatter <clang-formatter>"

to change the author of this commit.

OK. This worked. I can close this MR now. We can come back to this later.