Fix things broken from the last Atrac changes

Fixes:
   Yggdra Union (loading -> ingame)

Unbroken:
   Senjou no Valkyria 3 (had regressed)
   Savage Moon (had regressed)
   Wipeout Pure (had regressed)
   Ys Seven (had regressed)
   Canabalt (had regressed)
   PixelJunk Monsters (had started spewing errors to stdout, still played fine)

Still works:
   Lunar (locks up later still)
   Trails in the Sky (still seems playable now)

Still broken:
   Exit (dies when decode doesn't loop, but doesn't ask for a loop...)

-[Unknown]