Fixed filename in wxOSX-Cocoa's file dialog using extension of wrong file type.

Fixed filename in wxOSX-Cocoa's file dialog using extension of wrong file type.

When using SetFilterIndex to indicate a different initial file type the dialog would still use the extension of the first file type (if the filename had no extension then unchecking "Hide extension" would append the first file type's extension). Fixed this by calling code, that formerly got called only from OnFilterSelected, to notify OS X of the file type change.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67598 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775