RFR: [8] Bulk backports to sh/jdk8

[Roman Kennke]

> http://cr.openjdk.java.net/~shade/shenandoah/backports/jdk8u-20180514/webrev.01/
> 
> This backports recent work to sh/jdk8:
> 
>  [backport] Critical native tests should only be ran on x86_64 platforms
>  [backport] Fix Minimal VM build
>  [backport] Fixing Windows and ARM32 build
>  [backport] Fix ShFreeSet boundary case
>  [backport] Cleanup: removed unused code
>  [backport] Rename ShenandoahConcurrentThread to ShenandoahControlThread
>  [backport] Break heuristics out from ShCollectorPolicy into their own source files
> 
> Testing: hotspot_gc_shenandoah {fastdebug|release}
> 

make/excludeSrc.make:
+
+      Src_Files_EXCLUDE +=                                              \
+        shenandoahBarrierSet_x86.cpp

Don't we want that for _aarch64 files too?

Otherwise looks good!
Thanks, Roman