compiler: only finalize embedded fields before finalizing methods

compiler: only finalize embedded fields before finalizing methods

    When finalizing the methods of a named struct type, we used to
    finalize all the field types first.  That can fail if the field types
    refer indirectly to the named type.  Change it to just finalize the
    embedded field types first, and the rest of the fields later.

    Fixes golang/go#21253

    Reviewed-on: https://go-review.googlesource.com/52570

From-SVN: r250832