RFR: JDK-8222926: Unify cpu related part of shenandoahBarrierSetC1 and fix build when compiler1 is disabled

[Roman Kennke]

>>>> I changed the synopsis for the bug to: "Shenandoah build fails with --with-jvm-features=-compiler1"
>>>> -- please change it for the changeset you are pushing.
>>>
>>> Updated: http://cr.openjdk.java.net/~aoqi/8222926/webrev.05/
>>
>> This looks good. Thanks!
> 
> Thanks, Roman. I updated a new version. Do you agree with Aleksey and
> are you ok with the new version?

Yep, good!

Thanks,
Roman