tests: add data files for future wayland-scanner test

This patch adds the input and reference output data files for the
wayland-scanner tests to be added by the following patch.

The data files are split into their own patch because they are extremely
uninteresting to review:
- example.xml is just a copy wayland.xml from 1.12.0
- small.xml is a tiny dummy definition used for testing scanner
  variations without causing lots of big output files
- the other files are wayland-scanner products from the xml files

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Emilio Pozuelo Monfort <emilio.pozuelo@collabora.co.uk>
v2: update output due to 2c6350be
Acked-by: Yong Bakos <ybakos@humanoriented.com>