RFR [10], 2018-09-03, Bulk backports to sh/jdk10

[Roman Kennke]

> http://cr.openjdk.java.net/~shade/shenandoah/backports/jdk10-20180903/webrev.01/
> 
> This backports recent work to sh/jdk10:
> 
>  [backport] GC trace messages have to be immortal
>  [backport] Wiring GC events to JFR + Restore heap occupancy in GC logs after JFR changes
>  [backport] Remove obsolete/unused logging usages
>  [backport] Replace custom asserts with shenandoah_assert_*
>  [backport] Wiring heap and metaspace info to JFR
>  [backport] Out-of-cycle Degenerated GC should process references and unload classes
>  [backport] Off-by-one error in degen progress calculation
>  [backport] Check oop before pushing on Traversal queue
>  [backport] Only Java and GC worker threads should get GCLABs
>  [backport] Remove unused base_obj handling from closures and concurrent mark code
>  [backport] Move ParallelCodeIterator to ShenandoahCodeRoots
>  [backport] Evac reserve: make sure GC has untouchable space to move the objects into
>  [backport] Refactor FreeSet logging: support evac-reserve, denser printouts
>  [backport] Enable ShenandoahEvacReserveOverflow by default
> 
> Testing: tier3_gc_shenandoah {fastdebug|release}
> 
> Thanks,
> -Aleksey
> 

Very good, thank you!
Roman