This implements support for MWCC 4.1+ (aka GC 3.0a3 and above).
Notable changes:
- Hook `CreateFileMappingA` / `MapViewOfFile`: These compilers use these functions rather than `ReadFile` for headers.
- Hook `MultiByteToWideChar`: This function's behavior changed in Windows 2000 SP4 / Windows XP, and certain compiler versions rely on the old behavior. This fully reimplements it for CP-932 with the legacy behavior.
- Explicitly fail on invalid UTF-8 inputs. Add a warning log when the Shift JIS output is invalid.
