RFR: [8u] 2018-02-19: Bulk backports to sh/jdk8u

[Aleksey Shipilev]

http://cr.openjdk.java.net/~shade/shenandoah/backports/jdk8u-20180219/webrev.01/

This backports the bulk of improvements to sh/jdk8u:

b5a09ff17768: [backport] LotsOfCycles test timeouts
8735773ec619: [backport] Single thread-local GC state flag for all barriers
544322604347: [backport] ShConcurrentThread races with set_gc_state_bit
d55c6d5216d1: [backport] GC state testers (infra)
ab9dd1d11dc1: [backport] Protect C2 matchers with UseShenandoahGC
fd9724b26fdd: [backport] Refactor allocation failure and explicit GC handling
e5398dce6e7b: [backport] Make concurrent precleaning log message optional again
26b9048c042a: [backport] Make degenerated update-refs use region-set cursor to hand over work
12654193e434: [backport] Demote warning message about OOM-during-evac to informational
67294a38c0c7: [backport] TestSelectiveBarrierFlags should accept multi-element flag selections
ecb87af5e0d8: [backport] Implement flag to generate write-barriers without membars
b8c39bdc0dac: [backport] Log message on ref processing, class unload, update refs for mark events
bd01b07ba0d7: [backport] Add ShenandoahRootProcessor API to report threads while scanning roots
3a6457fecc72: [backport] Relax assert in SBS::is_safe()
f8aa59bf8732: [backport] Conditionalize PerfDataMemorySize on enabled heap sampling
240af491d9b5: [backport] Make major GC phases exclusive from each other
869aee37dbf1: [backport] Single GCTimer shared by all operations
dbdde8719baf: [backport] Don't treat allocation regions implicitely live during some GCs
9ea5ffefa388: [backport] Fix Mac OS build warnings
7c494d9db524: [backport] Record cycle start/end to avoid continuous periodic GC
437741c2bffd: [backport] Improve/more detailed timing stats for root queue work
f753dccda9dd: [backport] Fix/improve CLD processing
da727e3d353f: [backport] Use leftmost region in GC allocations
eef04e0a0474: [backport] Cleanup and strengthen BrooksPointer verification
35b65240dc8c: [backport] Remove BS:is_safe in favor of logged BS::verify_safe_oop
2a9afc3843f8: [backport] Rich assertion failure logging
2a3a44377445: [backport] Rename *_oop_static/oop_ref to *_forwarded
9fd8fc2e8b47: [backport] Get easy on template instantiations in ShConcMark
eada99b258fb: [backport] Improve assertion/verification messages a bit
00a3f7ca1c36: [backport] Demote ShenandoahAllocImplicitLive to diagnostic

Apart from very recent work in sh/jdk10, the only significant thing missing is Degenerated GC, which
gives me trouble in testing (I suspect another 8u-specific bug). I shall try and debug it for the
next bulk backport.

Testing: hotspot_gc_shenandoah {fastdebug|release}

Thanks,
-Aleksey