This little functional change uses the most common algorithm for panning
audio, known as constant power panning. It makes it so that the total
output power (not directly the sample value, i.e. the peak) stays the
same no matter how the audio is panned.
"Frame" is an MPEG term, which is not only unintuitive but also
overloaded with different meaning by other codecs (e.g. FLAC).
Therefore, use the standard term Sample for the central audio structure.
The class is also extracted to its own file, because it's becoming quite
large. Bundling these two changes means not distributing similar
modifications (changing names and paths) across commits.
Co-authored-by: kleines Filmröllchen <malu.bertsch@gmail.com>
