RFR: Upstream merge to jdk-12+21

[Roman Kennke]

jdk-12+21 arrived, let's merge up to it:

http://cr.openjdk.java.net/~rkennke/upstream-jdk12-merge-2018-11-22/outgoing.txt

Relevant changes:
- 8213615: GC/C2 abstraction for escape analysis
- 8213373: Bulk MarkBitMap clearing methods
- 8214027: Reinstate testB_mem_imm pattern in x86_64.ad
- 8213779: Loop opts anti dependent store detection should ignore
uncommon trap calls
- 8212070: Introduce diagnostic flag to abort VM on failed JIT compilation
- 8213746: GC/C2 abstraction for C2 matcher
- 8213992: Rename and make DieOnSafepointTimeout the diagnostic option
- 8213352: Separate BufferNode allocation from PtrQueueSet

Testing: Tier3_gc_shenandoah (release+fastdebug)

OK?
Roman