Fixed Windows drag'n'drop not showing insert position (STR #3209).

git-svn-id: file:///fltk/svn/fltk/branches/branch-1.3-porting@11132 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

src/fl_dnd_win32.cxx

@@ -134,6 +134,8 @@ public:
     }
     px = pt.x; py = pt.y;
     lastEffect = *pdwEffect;
+    // show insert position if dnd'ing in the same window/process (STR #3209)
+    Fl::flush();
     return S_OK;
   }
   HRESULT STDMETHODCALLTYPE DragLeave() {