Merge branch 'master' into jgrpp-beta

# Conflicts:
#	src/company_cmd.cpp
#	src/economy.cpp
#	src/lang/swedish.txt
#	src/network/network_command.cpp
#	src/news_gui.cpp
#	src/saveload/saveload.h
#	src/script/api/script_list.cpp
#	src/video/cocoa/cocoa_v.mm
#	src/video/sdl2_v.cpp

src/network/network_command.cpp

@@ -201,7 +201,7 @@ void NetworkSyncCommandQueue(NetworkClientSocket *cs)
 {
 	for (CommandPacket *p = _local_execution_queue.Peek(); p != nullptr; p = p->next) {
 		CommandPacket c = *p;
-		c.callback = 0;
+		c.callback = nullptr;
 		cs->outgoing_queue.Append(std::move(c));
 	}
 }