Initialize side and replay data so that replays work for MP games
launched from the command-line with the -m option.  This fixes bug #19877.
The code paths for command-line and lobby MP games are
entirely separate, so this has no effect on lobby games.

git-svn-id: http://svn.gna.org/svn/wesnoth/trunk@56036 75b3775d-3801-0410-9e12-e2e43121521d