1) Use IDynamicInvocationExpression for VB late bound invocation and C# dynamic invocation.
2) Use IDynamicIndexerAccessExpression for C# dynamic indexer access; not used in VB.
3) Remove IDynamicObjectCreationExpression.MemberName property.
4) Add extension methods on IHasDynamicArgumentExpression to get optional argument name and ref kind for an argument at a given index.