Avoid locking up the UI for gamecache loads.

If the icon/bg is not loaded yet, we'd lock and block for it to load
anyway.  This uses a separate (or possibly atomic) lock.
Warning fix.
On main screen, show game bgs using controller.

This won't affect touch UIs but it's a nice touch for controller based
animation imho.
Use flags to specify wanted data in gamecache.
Support PIC0 in PBP files.
Make it easy to get the SND0.AT3 data.