Resolve #723: Allow buffextras as a network-level module

modules/buffextras.cpp

@@ -75,6 +75,7 @@ public:
 
 template<> void TModInfo<CBuffExtras>(CModInfo& Info) {
 	Info.SetWikiPage("buffextras");
+	Info.AddType(CModInfo::NetworkModule);
 }
 
 USERMODULEDEFS(CBuffExtras, "Add joins, parts etc. to the playback buffer")