Add support for 3D Surround sound (5.1 + 7.1)

[Ras Talon]

Currently the game only seems to support stereo.

Adding options for various speaker configurations, the most common ones being 5.1 and 7.1 can add a whole new level of immersion.

[David Esparza Guerrero]

Fixed: Issue #392: Add support for 3D Surround sound (5.1 + 7.1)

→ <<cset 03b1c4fcdbd4>>