RFR: Small cleanup in node.hpp

[Roman Kennke]

I don't think we actually need to fwd-decl ShenandoahReadBarrierNode and
ShenandoahWriteBarrierNode in node.hpp because they are never used. We
only generate accessors for the more generic ShenandoahBarrierNode.

diff --git a/src/hotspot/share/opto/node.hpp
b/src/hotspot/share/opto/node.hpp
--- a/src/hotspot/share/opto/node.hpp
+++ b/src/hotspot/share/opto/node.hpp
@@ -143,8 +143,6 @@
 class SafePointNode;
 class SafePointScalarObjectNode;
 class ShenandoahBarrierNode;
-class ShenandoahWriteBarrierNode;
-class ShenandoahReadBarrierNode;
 class StartNode;
 class State;
 class StoreNode;


Testing: tier3_gc_shenandoah

Ok?

Roman