Codechange: make Subdirectory a scoped enum

src/newgrf_config.cpp

@@ -510,7 +510,7 @@ public:
 		}
 
 		GRFFileScanner fs;
-		int ret = fs.Scan(".grf", NEWGRF_DIR);
+		int ret = fs.Scan(".grf", Subdirectory::NewGrf);
 		/* The number scanned and the number returned may not be the same;
 		 * duplicate NewGRFs and base sets are ignored in the return value. */
 		_settings_client.gui.last_newgrf_count = fs.num_scanned;
@@ -654,5 +654,5 @@ std::string GRFBuildParamList(const GRFConfig &c)
  */
 std::optional<std::string> GRFConfig::GetTextfile(TextfileType type) const
 {
-	return ::GetTextfile(type, NEWGRF_DIR, this->filename);
+	return ::GetTextfile(type, Subdirectory::NewGrf, this->filename);
 }