1. don't assert if we're passed an empty defaultDir and full path in

1. don't assert if we're passed an empty defaultDir and full path in
   defaultFileName (the other ports don't do it)
2. don't duplicate gtk_file_chooser_set_current_folder() calls for
   save and open dialogs unnecessarily
3. reformated a couple of comments to fit in 80 columns

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@43863 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775