Fix two issues in new Befunge interpreter
Fix two issues in new Befunge interpreter

- Swap OP_GI and OP_GC so GI won't be used for `~'.
- It didn't compile with -Werror due to the lack of check for
  the return value of scanf.

shinh/elvm,shinh/elvm,ND-CSE-30151/elvm,shinh/elvm,shinh/elvm,shinh/elvm,shinh/elvm,ND-CSE-30151/elvm,ND-CSE-30151/elvm,shinh/elvm,shinh/elvm