Use COMMENT (not COMMENTS) as the category field to select songs when using SetPlayList.
Move FlightlessBird from Objects.ocd to Experimental.ocd.

Moved because it causes annoying errors on startup. It's not even a full definition and the material doesn't seem to be used anywhere.
Added GetPXSCount to docs.
Fix music fading when fading back to the same piece that is currently fading out.
Do not fade out music on scenario section loading.

Instead, scripters can use SetPlayList() or Music() to fade music by script if desired.
Added ambience test version of DeepSeaMining.