reflect: fix StructOf hash and string

reflect: fix StructOf hash and string

    Adjust the hash and string fields computed by StructOf to match the
    values that the compiler computes for a struct type with the same
    field names and types.  This makes the reflect code match the
    compiler's Type::hash_for_method and Type::reflection methods.

    Fixes golang/go#25284

    Reviewed-on: https://go-review.googlesource.com/116515

From-SVN: r261235