-Idle tick is now responsible for dispatching all pending sound sources, as such improves priority sorting.
-Added ui sound precache mechanisms (to fetch sounds without associated soundsources)
-Audio engine no logner available pre-login or upon disconnect, for simplicity.
-General cleanup to the audio engine/impl.
-Fixed some gAudiop calls that were lacking prerequisite null checks.
-Added 'isUpstreamOK' procuedure to LLAssetStorage to allow avoidance of making requests when there is no upstream host connection.
Looping sounds were always showing as 'Looping', even after they
stopped. Detection of stopped sounds is much better now.
Instead of only logging a sound as stopped when the audio source
is destroyed, we now detect whether or not it is associated with
an audio channel or not (the normal way to stop a sound is to set
the channel to NULL). This is still a bit fuzzy, since an
audio channel doesn't necessarily have to be playing, but states
where an audio source is associated with a non-playing audio channel
are only short temporary states that don't affect the usefulness
of the sound explorer.
