Rebase Thunderbird on top of 1:60.3.0-1~deb9u1

Some of https://security-tracker.debian.org/tracker/CVE-2018-12389, https://security-tracker.debian.org/tracker/CVE-2018-12390, https://security-tracker.debian.org/tracker/CVE-2018-12392 are rated critical or high impact by Mozilla becuase “evidence of memory corruption and we presume that with enough effort that some of these could be exploited to run arbitrary code”, “potentially exploitable crash”.

We’re not vulnerable to CVE-2018-12393 because we only support 64-bit.

Feature Branch: feature/16118-thunderbird-60.3.0

Original created by @intrigeri on 16118 (Redmine)

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information