Huge performance improvement: passing variables as pointers avoiding copies

src/variables/time.h

@@ -34,7 +34,7 @@ class Time : public Variable {
     explicit Time(std::string _name)
         : Variable(_name) { }
 
-    std::list<std::pair<std::string, std::string>>
+    std::list<ModSecurityStringVar *> *
         evaluate(Assay *assay) override;
 };