RFR (9): Backout parallel/merged synchronizer deflation and nmethod marking

[Roman Kennke]

We want to stabilize our jdk9 branch. I'm thus removing the
parallel/merged deflation and nmethod marking code because is this quite
experimental. It's in the JDK10 branch only now.

http://cr.openjdk.java.net/~rkennke/backout-deflation/webrev.00/
<http://cr.openjdk.java.net/%7Erkennke/backout-deflation/webrev.00/>

Tested: hotspot_gc_shenandoah

Roman