Breakpoint demolog, day 15: filters

Today I didn't implement the filter and its envelope, but I implemented the filter and fixed several bugs that had managed to get into the synth. Bad, bad guys!

No sample today, because I want to make the filter sound really phat. I am adjusting its parameter range and tweaking things here and there... Renoise's "Master spectrum" plot is coming quite handy for this, since I can spot where the resonance is happening and things like that, very easily.