A bunch of globals holding a reference to the xmpp-client. They should be also be unglobalized. {gui, game, game-view, net-server, net-client}
Some Engine functions are accessable from multiple ScriptInterfaces with different callback/private-data. I made the RegisterScriptFunctions a template of the callback-data type. That requires to #include "gui/CGUI.h" in more places.
Refs: #4211