don't define TRACE_CLIPBOARD in release builds (fixes gcc warning)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@42836 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/x11/clipbrd.cpp

@@ -32,10 +32,12 @@ Atom  g_clipboardAtom   = 0;
 Atom  g_targetsAtom     = 0;
 #endif
 
+#ifdef __WXDEBUG__
 // the trace mask we use with wxLogTrace() - call
 // wxLog::AddTraceMask(TRACE_CLIPBOARD) to enable the trace messages from here
 // (there will be a *lot* of them!)
 static const wxChar *TRACE_CLIPBOARD = _T("clipboard");
+#endif // __WXDEBUG__
 
 //-----------------------------------------------------------------------------
 // reminder