ErrorPosition indexed from 1

git-tfs-id: [http://falcon:8080/tfs/Projects]$/Phalanger/Main;C5140
Fix of exported types compilation
- Exported constructors defined *after* defining builders, so real types of typed parameters are resolved
- fix of DefineMethodExportStubs; .ctor defined on actual type, not its base in some cases

git-tfs-id: [http://falcon:8080/tfs/Projects]$/Phalanger/Main;C5141