RFR: 8259849: Shenandoah: Rename store-val to IU-barrier

[Zhengyu Gu]

On Fri, 15 Jan 2021 18:19:09 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

> We named the IU barriers StoreValEnqueueBarrier and various similar variations of this. Instead of naming it after how it's implemented, we should name it after its purpose: support IU-marking. It also looks confusing to have enqueue_barrier() and similar stuff, where no barrier is actually enqueued.
> 
> The renaming was 100% mechanical.
> 
> Testing:
>  - [ ] hotspot_gc_shenandoah (x86_64, x86_32, aarch64)

Some file's copyright year need to be updated. Otherwise, looks good.

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Marked as reviewed by zgu (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/2104