Adds player-location (positional audio) support to VoIP

Packages describing “mumble” as local USE flag

Package “mumble” Flag Description
games-fps/turtlearena Adds player-location (positional audio) support to VoIP
games-fps/urbanterror Use Mumble for ingame VoIP (experimental)
games-rpg/manaplus Enable support for voice chat

All packages providing a “mumble” USE flag (3)