[CSSolver] Property record opened pack expansion types

This is a bug which leads to accumulation of data in the constraint
system even though most of it is out of scope.

Author: xedin

lib/Sema/TypeOfReference.cpp

@@ -318,7 +318,7 @@ Type ConstraintSystem::openPackExpansionType(PackExpansionType *expansion,
                                            expansionVar, openedPackExpansion,
                                            expansionLoc));
 
-  OpenedPackExpansionTypes[openedPackExpansion] = expansionVar;
+  recordOpenedPackExpansionType(openedPackExpansion, expansionVar);
   return expansionVar;
 }