Start moving protocol-specific code to protocol.[ch]pp Move CMessageHeader from net.h to protocol.[ch]pp, with the implementation in the .cpp compilation unit (compiling once is enough). This commit does *not* and should not modify *any* code, it only moves it from net.h and splits it across protocol.cpp and protocol.hpp. Indentation changes aside the closest thing to a modification of code is the addition of the 'TODO' comment (the execution of which requires code modifications and thus doesn't belong in this commit). Signed-off-by: Giel van Schijndel <me@mortis.eu>