Fix gcc4.2 compile error. Patch by Simon Howes. b=450880 r=josh sr=roc

modules/plugin/base/src/nsPluginsDirDarwin.cpp

@@ -372,7 +372,7 @@ public:
     if (mRefNum > 0)
       ::CloseResFile(mRefNum);
   }
-  PRBool nsAutoCloseResourceObject::ResourceOpened()
+  PRBool ResourceOpened()
   {
     return (mRefNum > 0);
   }