Winamp 5.51 EQ changes

* New: Optional Constant-Q Equalizer and optional ISO Standard frequency bands

Configuration can found via: Winamp -> Prefs (Ctrl+P) -> Playback -> Equalizer tab

winamp.ini equivalent settings:

eq_type=1 (to use Constant-Q EQ)
eq_type=0 (to use Winamp 4Front EQ)
eq_frequencies=1 (for ISO frequency bands)
eq_frequencies=0 (for Winamp frequency bands)
eq_limiter=1 (to turn on clipping prevention) <-- currently for 4Front EQ only
eq_limiter=0 (to turn off limiter/clipping prevention)

ISO standard equalizer frequency table:
31.5, 63, 125, 250, 500, 1000, 2000, 4000, 8000, 16000

Winamp style EQ frequency table:
70, 180, 320, 600, 1000, 3000, 6000, 12000, 14000, 16000

Please note that the Frequency Band values will only change for the
Bento, Winamp Modern and Winamp Classic skins.

Until they've been updated accordingly, all other skins will only show
the Winamp frequency bands, even when the ISO bands are enabled.

Useful references/documentation: