Draft implementation for using clang's AST node visitor. (Not fully functional nor complete)

The current implementation is based on clang'sJSONNodeDumper, but the plan is to replace all the stringified properties with setting the raw data on nodes.

So this works like:

• <clang does node iteration>
• <clang callsVisit(const clang::<BaseType>*)> (eg.void ASTNodeVisitor::Visit(const Stmt* S))
• We callInnerStmtVisitor::Visit()
• <clang does inner node iteration>
• <clang callsVisit<MostDerivedType>>
• We override this visitor call (See visitor implementation startinghere)
• We check if the node has already been processed
• If not add a new node, and callConvert<MostDerivedType>(clang::<NodeType>, AST::<NodeType>)
• Convert... will then callConvert...Impl on itself and it's base types

• See the conversion implementations, startinghere
  • Also not that theConvert...Impl is the exact same code as is generated intoParseExpr/Stmt.h, in other words, with a little bit of work it should be possible to apply this for expr/stmt parsing right now