AGS: 7 Days A Skeptic - Audio volume issues

[antoniou79]

This is tested on Windows 10 x64, daily development build (ScummVM 2.4.0git186-g592f8b42c8 (Sep 8 2021 05:56:07)) and a local build (Windows, msys2, latest checkout from master).

Here are the issues I've noticed:

• The in-game sound volume controls which show up when putting the mouse cursor at the top of the screen do not seem to affect sound. There are two volume controls there, labelled "music" and "sound", and none of them affects sound (steps, ambient sound). However, I was not able to test them affecting music volume, since during intro when music is played, this in-game panel is not available.
• Setting the volume from the in-game controls is also not synched with any of ScummVM's own GMM sound options.
• Setting volume from the GMM, affects in-game sound only when changing the SFX volume. This affects both steps sound and ambient sound. The music (playing during intro) is not affected when changing music volume from GMM.