RFR [8]: 2018-09-25, Bulk backports to sh/jdk8u

[Aleksey Shipilev]

http://cr.openjdk.java.net/~shade/shenandoah/backports/jdk8u-20180925/webrev.01/

This backports recent work to sh/jdk8u:

 [backport] Disable ShHeapUncommit on too-large large-pages
 [backport] Fix call to is_g1_marking_load() with is_shenandoah_state_load() in ShenandoahSupport
 [backport] Purge some G1-related cruft in C2
 [backport] In update-refs, update all code-roots when in degen-gc
 [backport] Single marking bitmap
 [backport] Make sure bitmap is marked incomplete before bitmap resets
 [backport] Refactor bitmap cleaning
 [backport] Cleanup unused bitmap methods
 [backport] Improve liveness count during marking
 [backport] StringDedupMode enum for closures/method templates
 [backport] Fix indenting in ShMarkCompact::do_it
 [backport] Coarsen Full GC use of heap lock
 [backport] Micro-optimize ShHeap::get_region by moving the most likely branch first
 [backport] Print "process weakrefs" to disambiguate vs CM-with-UR
 [backport] Cleanup buffered queue handling
 [backport] Clean up dead code
 [backport] Remove Parallel Cleanup counters
 [backport] Clean up declarations and uses of marked_object_iterate
 [backport] Turn TestReferenceCAS into a standalone/no-testng test
 [backport] Homogenize unimplemented stubs handling
 [backport] Move ShenandoahAllocType and ShenandoahAllocRequest to separate file
 [backport] Inline ShHeap::prepare_concurrent_evacuation
 [backport] Remove ShHeap::region_in_collection_set in favor of SHR::in_cset
 [backport] Inline ShHeap::do_marked_object_complete
 [backport] Rename concurrentMark -> concurrent_mark
 [backport] Remove ShHeap::_heap_expansion_count
 [backport] Remove useless ShHeap::heap_region_iterate
 [backport] Inline trivial ShHeap methods right in header
 [backport] Code root iterators should not be instantiated in worker threads
 [backport] Record location when asserting the code root correctness
 [backport] Remove unused ShenandoahEvacuateRootsClosure
 [backport] Rename ShHeap::shenandoahPolicy -> ShHeap::shenandoah_policy
 [backport] Handle ShHeap::time_since_last_millis for RMI users
 [backport] Inline ShHeap::monitoring_support into header
 [backport] Sort ShenandoahHeap methods/fields into logical groups
 [backport] Silence VSC++ about multiple assignment operators
 [backport] Cleanup header files and forward declarations

Testing: hotspot_tier3_gc_shenandoah {fastdebug|release}

Thanks,
-Aleksey