This reverts commit 2fb58dc01c.
The original commit included an unexpected deletion of _all_
translations in certain languages. This was unintented, and appears to
have been a merging artefact.
This change will be re-submitted as a separate PR.
A long period of hand-editing caused these to fall out of sync with
what would have been generated from the source.
These were regnerated using the qt5_create_translation macro in the
root CMakeLists, and then using lconvert to merge the completely blank
translation files with the existing translations.
