- Partially reverts changes in 0b362afcc0
- Checks the codestring if its a valid game genie code before attempting
to decode it. If code fails, then assume it to be a pro action replay
cheat.
Issue: Cheats where failing because a value of 0 in the decoder does not
mean an error.
Fix https://github.com/libretro/libretro-fceumm/issues/384
Two issues are causiong PAR cheats to not work.
1. GG decoder should only accept specific characters. When it fails,
assume PAR code.
2. The corrent code that makes PAR decoding work was not set.
Both fixed on this PR with some added notes.