fix: some cleanup

include/util.h

@@ -41,6 +41,7 @@ void per_line(const char* file, line_handler handler);
 
 char* join(const char* a, const char* b);
 char* join3(const char* a, const char* b, const char* c);
+char* join4(const char* a, const char* b, const char* c, const char* d);
 
 const char* skip_arg(const char* cp);
 char* skip_spaces(const char* str);