There is no need to make type descriptors for named types when there
    are errors during package compilation.  Particularly, if the error in
    package compilation is from a malformed named type, there is no
    guarantee a type descriptor can be created.
    
    Fixes golang/go#11560.
    
    Reviewed-on: https://go-review.googlesource.com/12792

From-SVN: r226527