Little build fix to Windows ScRefreshTimer

For whatever reason "objdump.exe -t xicontent.o" on Windows now
lists Start@ScRefreshTimer@@EAEXXZ (probably because it's now
a virtual function). Also the reference to SetRefreshDelay
vanished after dropping the virtual keyword from SetRefreshDelay.

The linux object file doesn't even refer to a ScRefreshTimer
function. Start() can stay private, as the timer is handled via
SetRefreshDelay.

Probably Stop() should also become private in this case.

This also reverts 2c0189a8

Change-Id: I2a6900cd6bd76c4fec9f30131152b60a5bd2c2e7

sc/inc/refreshtimer.hxx

@@ -55,9 +55,11 @@ public:
     sal_uLong GetRefreshDelay() const;
     void StopRefreshTimer();
 
-    SC_DLLPUBLIC virtual void SetRefreshDelay( sal_uLong nSeconds );
+    void SetRefreshDelay( sal_uLong nSeconds );
     SC_DLLPUBLIC virtual void Invoke() SAL_OVERRIDE;
-    virtual void Start() SAL_OVERRIDE;
+
+private:
+    SC_DLLPUBLIC virtual void Start() SAL_OVERRIDE;
 };
 
 #endif // INCLUDED_SC_INC_REFRESHTIMER_HXX