Make mangler a class and reformat graph.

code/compiler/13/graph.hpp

@@ -17,6 +17,7 @@ struct group {
 using group_ptr = std::unique_ptr<group>;
 
 class function_graph {
+    private:
         using group_id = size_t;
 
         struct group_data {

code/compiler/13/mangler.hpp

@@ -2,8 +2,10 @@
 #include <string>
 #include <map>
 
-struct mangler {
+class mangler {
+    private:
         std::map<std::string, int> occurence_count;
 
+    public:
         std::string new_mangled_name(const std::string& str);
 };