[turbofan] Introduce an ExternalPointer type.

test/unittests/compiler/escape-analysis-unittest.cc

Index: test/unittests/compiler/escape-analysis-unittest.cc
diff --git a/test/unittests/compiler/escape-analysis-unittest.cc b/test/unittests/compiler/escape-analysis-unittest.cc
index c40dbab47bd0469588c292d1a3dc8dc1d7e79544..9cce5475fd2b287cee91d6e3c267304129169707 100644
--- a/test/unittests/compiler/escape-analysis-unittest.cc
+++ b/test/unittests/compiler/escape-analysis-unittest.cc
@@ -119,7 +119,7 @@ class EscapeAnalysisTest : public TypedGraphTest {
     if (!control) {
       control = control_;
     }
-    Node* zero = graph()->NewNode(common()->Int32Constant(0));
+    Node* zero = graph()->NewNode(common()->NumberConstant(0));
     return control_ = graph()->NewNode(common()->Return(), zero, value, effect,
                                        control);
   }