wayland: Pin Wayland protocol version

We need to be consistent among tests, bugs, etc against Wayland and Weston. I
think we all could develop and productize using the same version therefore, and
this CL attempts to do so.

Eventually we could build up a gyp option to set the desired version at
configuration time like use_wayland_version='1.4.0', but for now let's try to
pin one given version instead.