RFR (S) 8248240: Remove extendedPC.hpp and fetch_frame_from_ucontext

[Lois Foltan]

Looks good Coleen!
Lois

On 6/24/2020 5:08 PM, coleen.phillimore at oracle.com wrote:
> Summary: This empty interface was left over from deleting code from 
> before safepoint polling.
>
> See bug for details.  Ran tier1-3, and also builds on ppc, aarch64, 
> arm, s390, and zero.
>
> open webrev at http://cr.openjdk.java.net/~coleenp/2020/8248240.01/webrev
> bug link https://bugs.openjdk.java.net/browse/JDK-8248240
>
> Thanks,
> Coleen