We do that by adding support for a no_containers target which defines
the new option var/container/global_disable in rbm.conf. We already had
the option var/container/use_container doing something similar to this
new option, however it can not be overriden in rbm.conf as we define it
in each project's configuration, which has priority over rbm.conf.

Versions bump and Changelog update

Update rbm for #30039, adding support for the target_prepend and
target_append options in input_files.

In projects/https-everywhere/config we now use the target_prepend
option instead of the target option for the python input file.
This does not change the output of the build. However this makes it
possible in the future to check the channel or platform we build for
in the python project (which was not possible before as we were using
the target option, replacing all the initial targets).

Add bsaes as a new dependency of utls.

Wheezy is removed from deb.debian.org, so container image builds were
failing.

The jessie-backports suite has been removed from ftp.debian.org, so we
now download and install the package using snapshot.debian.org.

Fixes bug 29872 (XSS popup with DuckDuckGo search on about:tor)

Versions bump and Changelog update

We work around Mozilla's bug 1532530 (tracked in #29733).