Bug 24808: enable translation on results.js

Bug 24808: enable translation on results.js

String sorrounded by "__()"

To test:
1) create translation files for a language
(cd misc/translator; ./translate create xx-YY)

2) Check string
egrep -l "No cover image available" misc/translator/po/xx-YY-*
present in 2 files, opac-bootstrap and staf-prog

3) Apply patch

4) Create files again
(cd misc/translator; rm -f po/xx-YY*; ./translate create xx-YY)

5) Check again
egrep -l "No cover image available" misc/translator/po/xx-YY-*
present in 3 files, new in messages-js

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>