Add support for checkers not related to code formatting to the checkstyle.py script, and create a first checker that catches usage of the LOG() macro without an explicit category. Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com> Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>