Support for pre-v1.4 demo playback

Random number generator redesigned to reduce demo sync problems in future

'Q' key no longer ends demo recording

Allowing demos from any version wad to be loaded and run

Fixed internal demo sync problems (e.g. revenants)

Sound effects improved in spy mode -- hear what other player hears

Multiplayer spy mode shifts entire environment (status bar, viewpoint, sound, ...)

Spy mode (F12) allowed during Deathmatch demo playback

IPX networking and modem to current capabilities