... Doing the widening as needed to match Quality preference.
Fewer direct dependencies on QualityPrefs.h.
FLAC and OGG may import as float where before it was 24 bits; only 16 bits or
float. This makes them behave consistently with Raw and PCM.
... in four cases; not in some other .cpp file.
This is another move that causes the generated graph to reflect dependencies
correctly.
This fixes other large, hidden cycles that involved PrefsDialog.cpp: there was
link dependency on that when PrefsPanel.h was used for the base class. No
longer.
Also cycles involving TrackPanel.cpp, which contained the default
implementations for TrackPanelCell and related abstract base classes.
