sound/cem3340.cpp: Anti-aliasing. Streaming frequency and PW control.

[m1macrophage]

• Used the PolyBLEP algorithm for the ramp and pulse waves.
• Used the PolyBLAMP algorithm for the triangle wave.
• Made waveform outputs conditional on the output actually being connected.
• Added support for streaming control of the frequency control current and pulse width control voltage.

Effects of anti-aliasing:

• From top to bottom: ramp, pulse and triangle waveforms.
• Each spectogram shows a sequence of notes, increasing by 1 octave per step.
• Before (left column): the ramp and pulse waveforms suffered from significant aliasing. Aliasing on the triangle wave was only noticeable at high frequencies.
• After (right column): Significant reduction in aliasing on all waveforms. The ramp and pulse spectra look much cleaner, and the triangle is missing some of the "stray" harmonics in the top octaves.

[galibert]

Yay for band-limited oscillators :-)