Dynamic volume adjustment in xine

Hi Torsten!

Some two years ago I emailed you about changes made to xine post version 1.2.10 and how they 
affect Amarok 1.4 and Kaffeine distributed with TDE (successor of KDE3). The email thread was 
called "Problems with logarithmic volume scaling", started in late June 2023. I admit that back 
then I completely dropped the ball on this. Now I want to go back to one of the topics I raised 
in 2023, namely automatic volume adjustment during playback. Back then you wrote:

> When using xinue --verbose=2, you will get the explaination in the log,
> something like "Source too loud, adding -2.5dB declip filter.".
> For some technical background, see the comment in
> xine-lib-1.2/src/audio_dec/xine_mad_decoder.c, starting with
> "Report peak level _before_ clipping".
> The issue can (and should) be avoided by encoding mp3 with
> lame --scale=0.707 beforehand.

Would it be possible to add a runtime configuration option that makes this volume adjustment an 
opt-out behaviour? At the moment, the user experience is noticeably degraded because of this, 
because the volume lowers unexpectedly during playback. I don't think it is realistic to tell the 
users to re-encode their music collections with some specific `lame` settings. In my collection I 
estimate that around 80-90% of tracks are affected, and I know they play without issues on other 
players (vlc, mpv, standalone mp3 player). If this behaviour could be toggled on and off, we can 
than expose it via configuration to the users and let them decide whether they want this enabled 
or not.

Best regards,
Janek