Refactor code

It would seem I was wrong (was I drunk?). It doesn't support custom
message using formating (%s).
This simplifies things, as this stock is now meant to be used only on
predefined message.

* If not a predefined message, we redirect to client_print, as there is
more checks and can deal with ML.
* If length goes above known limits, we redirect to client_print to be
cut properly.
* Changed MSG_ONE to MSG_UNRELIABLE and MSG_ALL to MSG_BROADCAST.
* Updated documention.