After the gettext migration there is no point to have two
APIs for reading the same .mo file.

This patch is for sc/source/filter/ for easier review.

Change-Id: I77adc446e66623535a9d4c871ac1403e88efff78
Reviewed-on: https://gerrit.libreoffice.org/54183Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Julien Nabet <serval2412@yahoo.fr>