C++: Add failing test case for LargeParameter.ql

cpp/ql/test/query-tests/Critical/LargeParameter/LargeParameter.expected

@@ -1,3 +1,4 @@
 | test.cpp:16:13:16:14 | _t | This parameter of type $@ is 4096 bytes - consider passing a pointer/reference instead. | test.cpp:6:8:6:20 | myLargeStruct | myLargeStruct |
 | test.cpp:24:44:24:48 | mtc_t | This parameter of type $@ is 4096 bytes - consider passing a pointer/reference instead. | test.cpp:11:7:11:21 | myTemplateClass<myLargeStruct> | myTemplateClass<myLargeStruct> |
 | test.cpp:28:49:28:49 | b | This parameter of type $@ is 4096 bytes - consider passing a pointer/reference instead. | test.cpp:6:8:6:20 | myLargeStruct | myLargeStruct |
+| test.cpp:52:52:52:54 | rhs | This parameter of type $@ is 4096 bytes - consider passing a pointer/reference instead. | test.cpp:48:8:48:25 | CustomAssignmentOp | CustomAssignmentOp |

cpp/ql/test/query-tests/Critical/LargeParameter/test.cpp

@@ -44,3 +44,11 @@ void myFunction2(mySmallStruct *a, myLargeStruct *b) // GOOD
 void myFunction3(mySmallStruct &a, myLargeStruct &b) // GOOD
 {
 }
+
+struct CustomAssignmentOp {
+  // GOOD: it's an accepted pattern to implement copy assignment via copy and
+  // swap. This delegates the resource management involved in copying to the
+  // copy constructor so that logic only has to be written once.
+  CustomAssignmentOp &operator=(CustomAssignmentOp rhs); // FALSE POSITIVE
+  char data[4096];
+};