Huge performance improvement: passing variables as pointers avoiding copies

src/variables/time_wday.h

@@ -33,7 +33,7 @@ class TimeWDay : public Variable {
     explicit TimeWDay(std::string _name)
         : Variable(_name) { }
 
-    std::list<std::pair<std::string, std::string>>
+    std::list<ModSecurityStringVar *> *
         evaluate(Assay *assay) override;
 };