Fix non-POD in varargs.
Remove misleading max_players config variable (the engine doesn't care
about it, all the limits are hard-coded).
Remove civ-center-based player civ initialisation hack.
Add dummy player_defaults.json.
Clean up formatting a bit.
This was SVN commit r8498.
CGUI now represents a single 'page'. CGUIManager maintains multiple
pages and switches between them.
Split the XML files into pregame, loading, session and messagebox pages.
Added hotloading of GUI pages.
Minor GUI cleanups.
(Merge from hg 81862d33780c)
This was SVN commit r7214.
