introduce a CTRL_TAB_HEADER zone

Change-Id: If2740c91b9080cbbfe738b5235bc8612ab7580ba

include/vcl/salnativewidgets.hxx

@@ -84,8 +84,11 @@ typedef sal_uInt32      ControlType;
 // the active tab
 #define CTRL_TAB_PANE           55
 
+// The background to the tab area
+#define CTRL_TAB_HEADER         56
+
 // Background of a Tab Pane
-#define CTRL_TAB_BODY           56
+#define CTRL_TAB_BODY           57
 
 // Normal scrollbar, including
 // all parts like slider, buttons