Bug 22075: Fix encoding problem with RIS export in OPAC

Bug 22075: Fix encoding problem with RIS export in OPAC

When exporting a record with diacritics in RIS
format from the detail page in OPAC the encoding
is not correct and the diacritics appear broken.

This patch fixes it.

To test:
- Find or create a record with some special
  chars in your OPAC
- Go to the detail page
- Save as > RIS
- Verify the diacritics are broken in an editor
- Apply patch
- Repeat and verify everything now displays correctly

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
(cherry picked from commit bfeac6486516f185d9882d294d5000ab773c7dd5)
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>