[SystemInfo] Add Wayland support to get screen size

- Fix build on pure wayland platform using 'with_wayland' macro
  to distinguish x11 and wayland display systems.

- Add get_wayland_screen_size() method to retrieve the screen size in System_info API
  using native Wayland API.

Signed-off-by: Corentin Lecouvey <corentin.lecouvey@open.eurogiciel.org>
Merge pull request #254 from eurogiciel-oss/wayland_x11_display

Fix build on pure wayland platform