Documented wxMotif filedialog limitations WRT wildcard syntax.

Modified filedialog to either extract the wildcard (if only one wildcard
is present) or assert (if more than one is present).


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@18681 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

samples/dialogs/dialogs.cpp

@@ -457,7 +457,11 @@ void MyFrame::FileOpen(wxCommandEvent& WXUNUSED(event) )
                     _T("Testing open file dialog"),
                     _T(""),
                     _T(""),
+#ifdef __WXMOTIF__
+                    _T("C++ files (*.cpp)|*.cpp")
+#else
                     _T("C++ files (*.h;*.cpp)|*.h;*.cpp")
+#endif
                  );
 
     dialog.SetDirectory(wxGetHomeDir());