Fix window icon name (#696)

The icon is installed as "xreader".

Author: City-busz

shell/main.c

@@ -264,7 +264,7 @@ main (int argc, char *argv[])
 
 	ev_stock_icons_init ();
 
-	gtk_window_set_default_icon_name ("accessories-document-viewer");
+	gtk_window_set_default_icon_name ("xreader");
 	g_set_application_name (_("Document Viewer"));
 
     application = ev_application_new ();