Add volume gain on MumbleSetVolumeOverride and per player

Hello,

Currently with MumbleSetVolumeOverrideByServerId it is only possible to get up to 1.0.
It would be nice to have the ability to add some gain

Especially that with submix the overrided volume (at 1.0) is quite low compared to the volume of a player talking in front of you. This make radio calls complicated when near people talking. This was fine without submix but with it volume is now too low.

Even though the native documentation says it can be more than 1.0 it doesn’t sound louder with more than 1.0.

Also could be cool to have the possibility to add some volume gain on people without removing 3d and positional calculation. For example megaphone effect.

Thank you