C++: Fix iterator return types and accept test changes.

Author: MathiasVP

cpp/ql/test/library-tests/dataflow/taint-tests/standalone_iterators.cpp

@@ -66,8 +66,8 @@ class insert_iterator_by_trait {
     insert_iterator_by_trait operator++(int);
     insert_iterator_by_trait &operator--();
     insert_iterator_by_trait operator--(int);
-    insert_iterator_by_trait operator*();
-    insert_iterator_by_trait operator=(int x);
+    insert_iterator_by_trait& operator*();
+    insert_iterator_by_trait& operator=(int x);
 };
 
 template<>

cpp/ql/test/library-tests/dataflow/taint-tests/taint.expected

@@ -4,8 +4,5 @@ WARNING: Module DataFlow has been deprecated and may be removed in future (taint
 WARNING: Module DataFlow has been deprecated and may be removed in future (taint.ql:68,25-33)
 WARNING: Module TaintTracking has been deprecated and may be removed in future (taint.ql:73,20-33)
 testFailures
-| standalone_iterators.cpp:95:15:95:25 | // $ ast,ir | Missing result:ir= |
 | standalone_iterators.cpp:112:11:112:21 | // $ ast,ir | Missing result:ir= |
-| standalone_iterators.cpp:116:11:116:21 | // $ ast,ir | Missing result:ir= |
-| standalone_iterators.cpp:117:12:117:22 | // $ ast,ir | Missing result:ir= |
 failures