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

src/global-handles.cc

Index: src/global-handles.cc
diff --git a/src/global-handles.cc b/src/global-handles.cc
index a4b78ba07a8cec025757dac5ee0eade2ab02691e..6cc0cfb04eefef8b0db21ce216707be39db69c4c 100644
--- a/src/global-handles.cc
+++ b/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.