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That's what we do in most places, so let's be consistent.

In gettext-base < 1.8.2, like the one we had in Wheezy, gettext.sh
references the environment variable ZSH_VERSION, which we do not
set. This has prevented us from doing `set -u` in all gettext:ized
shell scripts unless we first initialize that variable before sourcing
gettext.sh.

Now that we install a new enough gettext-base, we can finally do this
and remove the initialization hacks.

Will-fix: #9371

Refs: #8064

The purpose of these settings was to show a green TorButton button in
the toolbar. Since this button is now hidden these settings can be
removed.

Will-fix: #8893

So it's not confused with Tor Browser's default search eninge,
Startpage.

So there's no chance it will try to use the Torified DNS server, in
case our firewall fails.

It makes a bit of sense on its own, and it guarantees that no weird
cruft in ~/.tor-browser will interfere for whatever reason.

No code is deleted/added/modified, only moved.

We could use `cp --no-dereference` before, when the TBB_EXT dir only
contained symlinks. This will reduce the memory footprint of the
chroot browsers, and incidentally fixed a bug where the
unsafe-browser's name wasn't set since we copied the langpack before
we fix the name in it.

Apparently the name is dictated completely by Torbutton, so
set_chroot_torbutton_browser_name() is enough. This should speed up
the start and reduce the memory footprint.

We don't have to any more (after the TBB migration) since we
explicitly set up the ones we want to use. This should speed up the
start and reduce the memory footprint.

We don't have to fix the name in all branding files, only for the
locale we're actually gonna use.

Extracting and then compressing the whole langpack/omni.ja isn't
necessary and takes a lot of time. Tests show a 50% reduction in
startup time.

After installing incremental upgrades Tails' root filesystem consists
of a stack squashfs:s, not only filesystem.squashfs. When not stacking
them correct we may end up using the Tor Browser (Firefox) from an
older version of Tails, or with no Tor Browser at all, as in the
upgrade from Tails 1.1.2 to 1.2, when we migrated from Iceweasel to
the Tor Browser.

Based on patch contributed by sanic.