how to add punctuation mark (or other things) at the end of lyric extender?

[Janek Warchoł]

Hi all,
i have a melisma at the end of a sentence, like here:

\version "2.13.45"
{
  \new Voice { c'8 d'4 e'8( c' f'4. g2 c'8 )}
  \addlyrics { ex -- ten -- der. __ }
}

i'd like the dot to appear after the extender (like in the bottom of
the attachment).
How can this be done? Manuals seem to say nothing about this, as well
as the mailing list archive.

cheers,
Janek

extender.png
Description: PNG image