CHANGE(client): Set min volume for pos. audio to 0

While in 0e43686 it was argued that
this setting should not be set to zero in order to avoid "bug" reports
of audio not working, because the volume of the audio has been zero due
to positional audio, setting this to anything but zero seems like
non-sense for such a feature.
Anything > 0 will lead to the player always being able to hear EVERY
player on the map, regardless of their position, whereas basically the
whole point of positional audio (in a "pure" sense) is to not have this
overlap of a million voices on a full game servers.

src/mumble/Settings.h

@@ -336,7 +336,7 @@ struct Settings {
  bool bPositionalHeadphone = false;
  float fAudioMinDistance = 1.0f;
  float fAudioMaxDistance = 15.0f;
- float fAudioMaxDistVolume = 0.25f;
+ float fAudioMaxDistVolume = 0.0f;
  float fAudioBloom = 0.5f;
  /// Contains the settings for each individual plugin. The key in this map is the Hex-represented SHA-1
  /// hash of the plugin's UTF-8 encoded absolute file-path on the hard-drive.