Refactoring on the operators: negation is now being handled globally

Other minors changes were also made, including adding the prefix `m_'
to all the members of the class.

src/operators/detect_sqli.cc

@@ -49,10 +49,6 @@ bool DetectSQLi::evaluate(Transaction *transaction, const std::string &input) {
         }
     }
 
-    if (negation) {
-        return issqli == 0;
-    }
-
     return issqli != 0;
 }