Add a new node, IIRFilterNode, that implements a general IIR filter. The coefficients are fixed at creation and not changeable with no automation functions allowed.
Docs: http://webaudio.github.io/web-audio-api/#the-iirfilternode-interface https://github.com/WebAudio/web-audio-api/issues/323 https://github.com/WebAudio/web-audio-api/pull/556