Refactor|libcommon: Switched p_xgsave.c to C++
Refactor|ACS|Hexen: Implement ACS state (de)serialization in C++, with Reader/Writer
Refactor|Hexen: Implement sound sequence (de)serialization with Reader/Writer
Refactor|XG|libcommon: Implement XG plane-mover (de)serialization in C++, with Reader/Writer
Merge branch 'master' of github.com:skyjake/Doomsday-Engine