Remove several grab-bag includes from the v8.h header.

src/globals.h

Index: src/globals.h
diff --git a/src/globals.h b/src/globals.h
index 41edb30835dcf72e81a5a4a7b45c8a1ae00c3ac5..5f1070382c199909fa87d7438ef86495575d3fad 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -515,6 +515,8 @@ enum VisitMode {
 // Flag indicating whether code is built into the VM (one of the natives files).
 enum NativesFlag { NOT_NATIVES_CODE, NATIVES_CODE };
 
+// JavaScript defines two kinds of 'nil'.
+enum NilValue { kNullValue, kUndefinedValue };
 
 // ParseRestriction is used to restrict the set of valid statements in a
 // unit of compilation.  Restriction violations cause a syntax error.