context suspend/resume

[ruby0x1]

Currently there is no way to globally suspend the audio context (this extends to processing as well as the backend calls to the API's).

This is important for many reasons, but the most important relates to using soloud on mobile platforms where the backgrounded app is disallowed interaction with the system in general. Web Audio, OpenAL, and other audio systems support the concept.

I've already discussed some details with jarikomppa this issue is simply for tracking and information purposes. I've started a naive implementation, for Null and OpenAL here but ran out of time. I hope to finish my implementation soon, but if there was a shorter and more correct path have at it!