Codechange: let GenerateDefaultSaveName return std::string

src/fileio_func.h

@@ -23,7 +23,7 @@ void FioCreateDirectory(const std::string &name);
 
 const char *FiosGetScreenshotDir();
 
-void SanitizeFilename(char *filename);
+void SanitizeFilename(std::string &filename);
 void AppendPathSeparator(std::string &buf);
 void DeterminePaths(const char *exe, bool only_local_path);
 std::unique_ptr<char[]> ReadFileToMem(const std::string &filename, size_t &lenp, size_t maxsize);