Clang format discussion

[ben.boeckel (Ben Boeckel (Kitware))]

I have a pending change into the robot to be able to just do the sweeping reformat, so updating in the future will be as easy as:

• make new version available on the bot
• prep a topic which changes format.clang-format=8 to =9
• make an empty commit for the robot to reformat the repo into
• run the reformatter until it hits a fix point