Convert save filenames to UTF-8

Fixes #6

src/system4.c

@@ -73,10 +73,12 @@ char *gamedir_path(const char *path)
 
 char *savedir_path(const char *filename)
 {
-	char *path = xmalloc(strlen(config.save_dir) + 1 + strlen(filename) + 1);
+	char *utf = sjis2utf(filename, 0);
+	char *path = xmalloc(strlen(config.save_dir) + 1 + strlen(utf) + 1);
 	strcpy(path, config.save_dir);
 	strcat(path, "/");
-	strcat(path, filename);
+	strcat(path, utf);
+	free(utf);
 	return path;
 }
 

src/vm.c

@@ -487,15 +487,7 @@ static void system_call(enum syscall_code code)
 	}
 	case SYS_EXISTS_SAVE_FILE: {
 		int slot = stack_pop().i;
-		struct string *name = heap[slot].s;
-		size_t dir_len = strlen(config.save_dir);
-		char *path = xmalloc(dir_len + 1 + name->size + 1);
-
-		strncpy(path, config.save_dir, dir_len);
-		path[dir_len] = '/';
-		strncpy(path+dir_len+1, name->text, name->size);
-		path[dir_len+1+name->size] = '\0';
-
+		char *path = savedir_path(heap[slot].s->text);
 		stack_push(file_exists(path));
 		heap_unref(slot);
 		free(path);