Packing sizes different than 4 caused offset mismatches (don't think any
garcs that were used the method were affected).
Trade off a small amount of packing speed to reduce memory footprint.
Use 1 filestream instead of 2 memorystreams.
Didn't bother to profile, but instead of ->ms->ms->arr, we ->fs->arr
Ends up using ~1GB repacking the Wild Encounter GARC, which should now
behave with 32bit systems.