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.

And use it consistently in all places instead of using the value as a
magic constant.

Merge branch 'bugfix/8158-stacked-rootfs-vs-chroot-browsers' into bugfix/7951-refactor-chroot-browsers

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.

This reverts commit 21540b34.

The proposed updates are now in Wheezy.

This reverts commit 3e80bd19.

The proposed updates are now in Wheezy.