This now prints each (format, modifier) tuple, to show which ones the
compositor sends to its clients. It is only implemented for version 3+,
since I didn’t have any compositor implementing previous versions, and
the old `format` event is deprecated anyway.
Signed-off-by: Emmanuel Gil Peyrot <emmanuel.peyrot@collabora.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>