Implement wxFontDialog::SetTitle() in wxMSW

Base class SetTitle() implementation didnd't work for this class as it
used the (invalid) HWND of not yet existing dialog, so add a hook
procedure for the common font dialog, similar to the existing one for
wxColourDialog, which allows us to set the dialog title when the dialog
is really created.

Closes https://github.com/wxWidgets/wxWidgets/pull/865

Closes #18177.

include/wx/msw/fontdlg.h

@@ -25,8 +25,12 @@ public:
         : wxFontDialogBase(parent, data) { Create(parent, data); }
 
     virtual int ShowModal() wxOVERRIDE;
+    virtual void SetTitle(const wxString& title) wxOVERRIDE;
+    virtual wxString GetTitle() const wxOVERRIDE;
 
 protected:
+    wxString m_title;
+
     wxDECLARE_DYNAMIC_CLASS_NO_COPY(wxFontDialog);
 };