Hi Guix,

here are two patches to improve our handling of po files. Yesterday I
pushed again new po files that were broken, and I didn't notice. The
first patch ensure po files are normalized. The TP automatically
normalized po, but weblate doesn't, using the indent method instead.
This creates huge patches like yesterday. Instead, normalizing ensures
we only see relevant changes.

The second patch adds a check-po target to the Makefile that runs
msgfmt on every po file we have, to make sure they are at least
correct. That's not enough for manual translations, but that can be
spotted easily when running "make". This would have spotted the issues
I introduced yesterday.