Implement NesCore with FCEUmm/Nestopia/Mesen libretro core support.
Generalize native frontend to handle cores that require ROM data in
memory (need_fullpath=false) and move PS1-specific config out of C++
into Ps1Core. Bundle both core .so files as APK assets with automatic
extraction. Fix cover art fetching for GoodNES-named ROMs by expanding
region codes (U)->(USA, Europe) to match LibRetro thumbnail naming.
Matt Hills
d502304d95