Firstly this changes the type of parent map to be keyed on DynTypedNode to
simplify the following changes. This comes with a DenseMapInfo for
DynTypedNode, which is a bit incomplete still and will probably only work
for parentmap right now.
Then the RecursiveASTVisitor in ASTContext is updated and finally
ASTMatchers hasParent and hasAncestor learn about the new functionality.
Now ParentMap is only missing TemplateArgumentLocs and CXXCtorInitializers.