requiring all .po files be UTF8-encoded

Hello,

There's an ongoing project to add a regression test to ensure all
platforms are correctly handling translations. [1]

[1] https://postgr.es/m/b292844.1765315339@sss.pgh.pa.us

The conversation there is leading to requiring all translation files use
UTF-8 encoding. In practice all live files already are UTF8 [2], so
there's no new requirement; but I think we should add some enforcing
mechanism (maybe a git hook and/or the website-building script refusing
to use a nonconformant file) to ensure we don't break things going
forward.

We can trivially convert all existing files with this oneliner:

for i in $(git grep 'Content-Type:' | grep -v UTF-8 | cut -d: -f1); do msgconv -t UTF-8 $i | sponge $i; done

[2] Actually there is one exception -- nb/pg_config.po. However, this
file is under the 80% translation requirement, so it should be removed;
moreover the Norwegian translation seems abandoned, having been done for
7.4, with a single update for 8.1 (pg_config.po) and never again touched.
Maybe we should remove all these files.

We have a few more dead languages: af fa fe fr fy id nl sk sl ta ro.
I guess we display those in our translation table out of a stubborn
expectation that translators will magically show up. I think I would
rather hide those and not take up screen space -- maybe write two pages,
the normal main one without those languages, and a separate one that
includes them.

--
Álvaro Herrera Breisgau, Deutschland — https://www.EnterpriseDB.com/