MGASA-2020-0378 Updated Thunderbird packages fix security vulnerabilities

AppCache manifest poisoning due to url encoded character processing CVE-2020-12415. Use-after-free in WebRTC VideoBroadcaster CVE-2020-12416. Integer overflow in nsJPEGEncoder::emptyOutputBuffer CVE-2020-12422. WebRTC permission prompt could have been bypassed by a compromised content process...