bug 3161: don't display blank language chooser

bug 3161: don't display blank language chooser

If more than one translation is installed but only one is active, a blank div
is displayed at the bottom of all pages in the intranet (and in the OPAC if the
opacchangelanguages system preference is ON), taking a bit of vertical real
estate needlessly.

Changed so that <div> for the language chooser is output
only if there is more than one enabled language.

Signed-off-by: Galen Charlton <galen.charlton@liblime.com>
Signed-off-by: Henri-Damien LAURENT <henridamien.laurent@biblibre.com>