Minor improvements and updates
- Upgrade tor to 0.3.4.9-1~d90.stretch+1.
- Upgrade Mesa to 18.2.6-1~bpo9+1, libdrm to 2.4.95-1~bpo9+1,
and libglvnd to 1.1.0-1~bpo9+1.
- Upgrade firmware-linux and firmware-nonfree to 20190114-1.
- Upgrade amd64-microcode to 3.20181128.1.
- Upgrade intel-microcode to 3.20180807a.2~bpo9+1.
- Remove the boot readahead feature (Closes: #15915).
In most supported use cases, it did not improve boot time anymore,
or even increases it.
- Require TLS 1.2 in our Upgrader and zerotracepen-security-check (Closes: 11815).
- Enable O_CREAT restriction in /tmp directories for FIFOs and regular
files (Closes: #16072).
- Upgrade systemd to 240-4~bpo9+0zerotracepen1 (Closes: #16352).
Fixes CVE-2018-16864, CVE-2018-16865, and CVE-2018-16866.
- Upgrade Enigmail to 2.0.8-5~deb9u1 (Closes: #15657).
- Upgrade Torbirdy to 0.2.6-1~bpo9+1 (Closes: #15661).
- Modify Torbirdy configuration in a way that's easier to maintain.
- Tell the user they need to use sudo when they attempt to use su
(Closes: #15583).