Where is crystalspace.sndsys.manager?

[LigH]

When I run the Windows client 0.3.012 from a console window, I can read

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WARNING: could not load plugin \'crystalspace.sndsys.manager\'
In which file is this class included? If I knew, I could try to make this file update. It does not seem to be vital, though - in-game sound effects still work.