Common header file between mvdsv and ezquake

[Lee Garrett <debian@rocketjump.eu>]

Hi,

while packaging mvdsv 1.00 I noticed that src/protocol.h is not shipped anymore, 
which makes the build fail.

I checked the git repo why it was removed, and it is now hosted in a separate 
repo: https://github.com/QW-Group/qwprot

This header file is also used in ezquake builds. Does it make sense to package 
this separately as e.g. qwprot-dev, and let ezquake build on it, too? Or should 
we go with the easier route and just duplicate it in both packages, at the risk 
that they might diverge?

Regards,
Lee