[Freeciv-Dev] (PR#13648) Turn done in online games bug

["Jason Short" <jdorje@xxxxxxxxxxxxxxxxxxxxx>]

<URL: http://bugs.freeciv.org/Ticket/Display.html?id=13648 >

If you click on turn done near the end of the turn, but by the time the
server receives the packet it has already started end-of-turn
processing, then the server won't process the packet until the next turn
and will treat it as your end-of-turn for the next turn.  This is a
problem with all packets (moving units, etc.) but is especially bad for
the turn-done packet.

In the development version this behavior is improved (PR#13185).  The
turn # is added to the turn-done packet and the server uses it for
sanity checking.  Similar sanity checks could be added to other packets:
for instance a move-unit and unit-orders packet could sanity check the
position of the unit to prevent the bug where you stop a goto during
end-turn, issue new movement/orders, but since these new commands don't
take effect until the next turn the unit will already have taken its
next goto steps and will be desynched.

These patches could be backported to 2.0, with an optional capability. 
Would this be worthwhile?  How serious is this problem?

-jason