RFR: Clean up differences against upstream

[Aleksey Shipilev]

I see the post-merge differences here:
  https://builds.shipilev.net/patch-openjdk-shenandoah-jdk/

Strdedup tests are still in quarantine, and there is a minor whitespace difference. I basically
"patch -p1 -R"-ed the webrev above, omitting .hgtags change:

diff -r db8467d25e8b src/hotspot/share/gc/shenandoah/c2/shenandoahSupport.hpp
--- a/src/hotspot/share/gc/shenandoah/c2/shenandoahSupport.hpp  Thu Apr 11 11:40:30 2019 +0200
+++ b/src/hotspot/share/gc/shenandoah/c2/shenandoahSupport.hpp  Thu Apr 11 12:20:10 2019 +0200
@@ -47,4 +47,5 @@
     ShenandoahNone,
   };
+
   static bool verify_helper(Node* in, Node_Stack& phis, VectorSet& visited, verify_type t, bool
trace, Unique_Node_List& barriers_used);
   static void report_verify_failure(const char* msg, Node* n1 = NULL, Node* n2 = NULL);
diff -r db8467d25e8b test/hotspot/jtreg/ProblemList.txt
--- a/test/hotspot/jtreg/ProblemList.txt        Thu Apr 11 11:40:30 2019 +0200
+++ b/test/hotspot/jtreg/ProblemList.txt        Thu Apr 11 12:20:10 2019 +0200
@@ -138,11 +138,4 @@
 #############################################################################

-# :hotspot_gc_shenandoah
-
-gc/shenandoah/TestStringDedup.java                            8220671,8221102 generic-all
-gc/shenandoah/TestStringDedupStress.java                      8220671,8221102 generic-all
-
-#############################################################################
-
 # :hotspot_misc


Testing: hotspot_gc_shenandoah

-- 
Thanks,
-Aleksey