Add an example of customizing "Save" file dialog too

Show doing it in the sample and also add a missing line to the example
in the documentation.

interface/wx/filedlgcustomize.h

@@ -331,6 +331,7 @@ public:
         // This object may be destroyed before the dialog, but must remain
         // alive until ShowModal() returns.
         EncryptHook customizeHook;
+        dialog.SetCustomizeHook(customHook);
 
         if ( dialog.ShowModal() == wxID_OK )
         {

samples/dialogs/dialogs.cpp

@@ -2009,10 +2009,42 @@ void MyFrame::FileSave(wxCommandEvent& WXUNUSED(event) )
 
     dialog.SetFilterIndex(1);
 
+    // This tests the (even more simplified) example from the docs.
+    class EncryptHook : public wxFileDialogCustomizeHook
+    {
+    public:
+        EncryptHook()
+            : m_encrypt(false)
+        {
+        }
+
+        void AddCustomControls(wxFileDialogCustomize& customizer) wxOVERRIDE
+        {
+            m_checkbox = customizer.AddCheckBox("Encrypt");
+        }
+
+        void TransferDataFromCustomControls() wxOVERRIDE
+        {
+            m_encrypt = m_checkbox->GetValue();
+        }
+
+        bool Encrypt() const { return m_encrypt; }
+
+    private:
+        wxFileDialogCheckBox* m_checkbox;
+
+        bool m_encrypt;
+    };
+
+    EncryptHook customHook;
+    dialog.SetCustomizeHook(customHook);
+
     if (dialog.ShowModal() == wxID_OK)
     {
-        wxLogMessage("%s, filter %d",
-                     dialog.GetPath(), dialog.GetFilterIndex());
+        wxLogMessage("%s, filter %d%s",
+                     dialog.GetPath(),
+                     dialog.GetFilterIndex(),
+                     customHook.Encrypt() ? ", encrypt" : "");
     }
 }