RFR [11u]: Bulk backports to sh/jdk11

[Roman Kennke]

Looks good to me. Thanks!

Roman

> Pick up another batch of simple sh/jdk11 backports:
>   [backport] 8220664: Simplify ShenandoahUpdateHeapRefsClosure
>   [backport] 8222403: Shenandoah: Remove ShenandoahAlwaysTrueClosure, use AlwaysTrueClosure instead
>   [backport] 8222425: Shenandoah: Move commonly used closures to separate files
>   [backport] 8222843: Print Shenandoah cset map addresses in hs_err
>   [backport] 8222838: Shenandoah: SEGV on accessing cset bitmap for NULL ptr
> 
> Webrev:
>    http://cr.openjdk.java.net/~shade/shenandoah/backports/jdk11-20190426/webrev.01/
> 
> Testing: hotspot_gc_shenandoah {fastdebug,release}
>