Fix bit field for GlobalHandles::Node State in MSVC.

TBR=vitalyr@chromium.org
BUG=1243
TEST=none

Review URL: http://codereview.chromium.org/6658040

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7136 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/global-handles.cc

@@ -210,7 +210,7 @@ class GlobalHandles::Node : public Malloced {
     NEAR_DEATH,  // Callback has informed the handle is near death.
     DESTROYED
   };
-  State state_;
+  State state_ : 4;  // Need one more bit for MSVC as it treats enums as signed.
 
  private:
   // Handle specific callback.