C++: Define the argv flow source in terms the input parameter

Author: jketema

cpp/ql/lib/semmle/code/cpp/security/FlowSources.qll

@@ -92,7 +92,7 @@ private class ArgvSource extends LocalFlowSource {
     exists(Function main, Parameter argv |
       main.hasGlobalName("main") and
       main.getParameter(1) = argv and
-      this.asExpr() = argv.getAnAccess()
+      this.asParameter() = argv
     )
   }