tr2/savegame: save and load current music

This allows the current music track and position to be saved and
restored on load, similar to TR1X.

Resolves #2579.

docs/tr2/CHANGELOG.md

@@ -11,6 +11,7 @@
 - added BSON savegame support, removing the limits imposed by the OG 8KB file size, so allowing for storing more data and offering improved feature support (legacy save files can still be read, similar to TR1) (#2662)
 - added NG+, Japanese, and Japanese NG+ game mode options to the New Game page in the passport (#2731)
 - added the ability for spike walls to be reset (antitriggered)
+- added the current music track and timestamp to the savegame so they now persist on load (#2579)
 - added waterfalls to the savegame so that they now persist on load (#2686)
 - changed savegame files to be stored in the `saves` directory (#2087)
 - changed the default fog distance to 22 tiles cutting off at 30 tiles to match TR1X (#1622)

docs/tr2/README.md

@@ -303,6 +303,7 @@ as Notepad.
 
 #### Audio
 - added an option to control how music is played while underwater rather than simply muting it
+- added the current music track and timestamp to the savegame so they now persist on load
 - fixed music not playing with certain game versions
 - fixed the audio not being in sync when Lara strikes the gong in Ice Palace
 - fixed sound settings resuming the music