Gracefully fallback when xkb context creation fails

xkb context creation can fail when xkeyboard-config files are not
available.

This changes qwlkeyboard to gracefully fallback on the
QT_NO_WAYLAND_XKB path, as suggested by Giulio Camuffo.

Change-Id: Ic57d80b6aa3e9fbd8a393a3ca54dff768a4c3e83
Reviewed-by: Giulio Camuffo <giulio.camuffo@jollamobile.com>
Update .gitignore after wayland examples move

Change-Id: I44e0dc6ac4e92a8bdc6a9f8398e60e4d323247f9
Reviewed-by: Giulio Camuffo <giulio.camuffo@jollamobile.com>