Thanks Anssi and Tim for reviews.

Backport of 8780849d from master

Backport of 865bc717 from master

Backport of 9f18b6bc from master

test_i18n_language_non_english_fallback fails if run after
test_L10N_deactivated; the tests can be run in any order after
a5f6cbce but this commit is not
in stable/1.7.x.

Backport of 136a3ffe from master

Backport of fddd9525 from master

Thanks brylie.

Backport of 89b9e6e5 from master

Thanks Diego Cerdán for the suggestion.

Backport of 54546cee from master

Backport of 2c1384fb from master

Thanks haimunt at yahoo.com for the suggestion.

Backport of e6b3d6c2 from master

Refs #9722. Thanks Tim Graham for the review.
Backport of 6d302f63 from master.

Thanks Collin Anderson for the report and original patch.

Backport of 2572c07c from master

Backport of 67f9f385 from master

Backport of ab431fbd from master

Backport of 86c74eac from master

Backport of fff7b507 from master

Thanks to antialiasis at gmail dot com for the patch.

Refs #22950.
Backport of 92090492 from master.

This patch also fixes update_error_dict to better handle the use case described
in this ticket, previously the type of the provided container could be lost in
some conditions.

Thanks Russell Keith-Magee for the report and Tim Graham for review.

Backport of eb7df6b8d7 from master

Thanks raphael.herouart at gmail.com

Backport of 814bcc33 from master

Thanks Claude Paroz.

Backport of 1a3bec4a from master

Thanks projectgus for the suggestion.

Backport of c37000ab from master

Backport of 5842d8eb from master

Thanks mila for the suggestion.

Backport of db9a1a0c from master

Translators may want to change the irc link pointing to a
language-specific channel.
Backport of 232f2028 from master.

Thanks scibi for the report.

Backport of bbf0a954 from master

Thanks mrknacky at gmail.com for the report and gajimenezmaggiora
for the draft patch.

Backport of e3c7af18 from master

Thanks cjerdonek for the suggestion.

Backport of 874053ed from master

Backport of 0b5bafe9 from master

Backport of 5359188b from master

Backport of add78c58 from master

Backport of 4c39c270 from master

Backport of 70576740 from master

Backport of 1e841125 from master