use generic file picker in wxFLP_SAVE case as the native one doesn't allow to select non-existent files

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_8_BRANCH@51620 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk/filepicker.cpp

@@ -41,7 +41,9 @@ bool wxFileButton::Create( wxWindow *parent, wxWindowID id,
                         long style, const wxValidator& validator,
                         const wxString &name )
 {
-    if (!gtk_check_version(2,6,0))
+    // we can't use the native button for wxFLP_SAVE pickers as it can only
+    // open existing files and there is no way to create a new file using it
+    if ( !(style & wxFLP_SAVE) && !gtk_check_version(2,6,0) )
     {
         // VERY IMPORTANT: this code is identic to relative code in wxDirButton;
         //                 if you find a problem here, fix it also in wxDirButton !