dvdnav: also probe file:// (fixes #2131)

(cherry picked from commit fd0cff6a)

Conflicts:

	modules/access/dvdnav.c

modules/access/dvdnav.c

@@ -97,6 +97,7 @@ vlc_module_begin();
     set_capability( "access_demux", 5 );
     add_shortcut( "dvd" );
     add_shortcut( "dvdnav" );
+    add_shortcut( "file" );
     set_callbacks( Open, Close );
 vlc_module_end();