To implement a MOD variant for the Chewy engine, this commit makes some changes
to make subclassing of the ProtrackerStream and associated Module class easier.
Add support for dividing the playing rate of Paula and SoundFx audio
by integers other than 1. This is going to be used in the Cine engine
for dividing the playing rate of music in the Amiga version of Operation
Stealth by 2 to get it to sound right. Otherwise it sounds too high
pitched.
This is groundwork for fixing bug #11676.
Paula low-pass filtering, as implemented by UAE.
The Amiga has two filtering circuits: a static RC filter
(only) on the A500, and an LED filter that can be enabled
or disabled dynamically.
By default, the Paula now doesn't apply the static RC
filter, but allows for enabling the LED filter (with
setAudioFilter()).
NOTE: At the moment, this code still uses floating point
arithmetics! It also calls tan() three times per
instantiation.
