C2: add SafePointScalarObjectNodes from ValueTypeNodes to SafePointNodes without an allocation + propagate materialized value type in the graph

[Roland Westrelin]

> Finally, I noticed WhiteBox.deoptimize() doesn't work properly. That
> will need to be fixed in jdk9 as well apparently (I can take care of
> it).

Actually it was removed from jdk9 so I'll use:

diff --git a/test/compiler/valhalla/valuetypes/ValueTypeTestBench.java b/test/compiler/valhalla/valuetypes/ValueTypeTestBench.java
--- a/test/compiler/valhalla/valuetypes/ValueTypeTestBench.java
+++ b/test/compiler/valhalla/valuetypes/ValueTypeTestBench.java
@@ -356,7 +356,7 @@
         MyValue v = MyValue.createInline(rI, rL, rD);
         if (flag) { 
             // uncommon trap
-            WHITE_BOX.deoptimize();
+            WHITE_BOX.deoptimizeMethod(tests.get("ValueTypeTestBench::test16"));
         }
         return sumValue(v);
     }

Roland.