Fixed: savegames didn't store the player's spectator status.

When loading a savegame, if the player was a (dead) spectator, that information gets lost. What ends up happening is the player inherits the properties of a spectator upon loading the game, but isn't actually spectating. This causes some weird behaviour and the source-like spectating mode also breaks.

With this fix, their (dead) spectator status now gets serialized when saving/loading a game. Since only the local player remains in offline savegames, if they were a dead spectator, they will be turned into a true spectator when the game is loaded, which seems to be the best way to handle this without running into unforeseen edge cases.