Improve sound effect quality (digitized sounds)

[lethal-guitar]

~Many of the digitized sound effects don't sound on-par with what DosBox outputs, they are too quiet and missing high frequencies. Also,~ there are clicking/popping issues with quickly repeated sound effects.

There are two aspects of this problem:

• ~ADPCM-decoding: It's worth seeing how the decoder from DosBox compares to the current one.~
• Cross-fading when re-triggering sound effects (to get rid of clicks/pops)

~Then, it might also be good to look into alternative resampling approaches.~