7175911: Simplify error reporting API in Check.CheckContext interface
Summary: Make error messages generated during Check.checkType more uniform and more scalable
Reviewed-by: jjg, dlsmith

7151492: Encapsulate check logic into Attr.ResultInfo
Summary: ResultInfo class should be used to make attribution code transparent w.r.t. check logic being used
Reviewed-by: jjg, dlsmith

7002070: If catch clause has an incompatible type, error pointer points to first exception type in list
Summary: Attribution should check each component of a disjunctive type separately, rather than checking the corresponding lub()
Reviewed-by: jjg