Allow loading game info without clearing old.

More seamless when we already have the icon, for example.
Refactor a bit to simplify the code.
Load the icon on the game screen with the bg.

Still looks nicer this way.
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.
Merge pull request #6388 from unknownbrackets/ui-tweaks

Show game background during controller/keyboard game selection