Chain %d->%F->%f in the attachment menu.
Previously, %d would use %f if there was no description set.
Place the new %F option in between %d and %f. This way, %d will fall
back on %F, which will fall back on %f. This allows the standard
attachment menu to show d_filename.
This is useful for forwarding attachments or editing draft files with
attachments. In these cases the actual filename is sanitized but the
attachment name is preserved in d_filename.