protocol compatibility issue

[Shuang He]

Hi, all
     Have you met issue that, only updating wayland while not rebuilding 
weston, mesa, it will not work. It may due to wayland protocol is 
updated, which will need to update weston and mesa as well.
     Is there any protocol version check policy applied? I'd like to be 
told that 'protocol is incompatible' instead of trying pull and 
rebuilding everything.
     This may also be helpful for doing bisect.

Thanks
     --Shuang