added wxFileStream::IsOk() (patch 1749587)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@47267 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/wfstream.h

@@ -116,6 +116,7 @@ class WXDLLIMPEXP_BASE wxFileStream : public wxFileInputStream,
 {
 public:
     wxFileStream(const wxString& fileName);
+    virtual bool IsOk() const;
 
 private:
     DECLARE_NO_COPY_CLASS(wxFileStream)