This reverts commit 294674c5,
that was apparently created using a newer version of po4a
than what our website requires.

Currently translated at 17.7% (11 of 62 strings)

Translation: Tails/wiki/src/news/version_3.14.1.*.po
Translate-URL: http://translate.tails.boum.org/projects/tails/wikisrcnewsversion_3141po/pt/

Currently translated at 39.0% (16 of 41 strings)

Translation: Tails/wiki/src/news/version_3.11.*.po
Translate-URL: http://translate.tails.boum.org/projects/tails/wikisrcnewsversion_311po/it/

This reverts commit 0dac4d38.

Currently translated at 70.8% (17 of 24 strings)

These used to say "Icedove (Thunderbird)" which wasn't handled so
nicely by s/Icedove/Thunderbird/.

This is just a massive 's/Icedove/Thunderbird/' both in terms of
content and filenames. No logic is changed, which should ease
reviewing of this massive commit.

Will-fix: #12242

Add sort="age" to inline directives in PO files, to avoid making hundreds of strings fuzzy (refs: #12053).