Audio fixes round 2

Grants position and velocity data to Audible components, as they were
intended to be independent of others to begin with.

Mixer now auto-updates the position attribute of all playing Audible
components.

Mixer no longer consumes a full core.

Process tracks time in nanoseconds since last foreground execution.  Use
protected method delta() to compute.

Titania.buffer() method signature changed to match Titania.array().