Introduce helper test code to implement the client side of the
input_timestamps_unstable_v1 protocol. This helper will be used in
upcoming commits to test the server side implementation of the protocol
in libweston.

The input_timestamps_unstable_v1 protocol was introduced in version 1.13
of wayland-protocols, so this commit updates the version dependency in
configure.ac accordingly.
Signed-off-by: Alexandros Frantzis <alexandros.frantzis@collabora.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>