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 (CVE-2020-12424). Out of bound read in Date.parse() (CVE-2020-12425). Memory safety bugs fixed in Thunderbird 78 (CVE-2020-12426). X-Frame-Options bypass using object or embed tags (CVE-2020-15648). Memory safety bugs fixed in Thunderbird 78.3 (CVE-2020-15673). XSS when pasting attacker-controlled data into a contenteditable element (CVE-2020-15676). Download origin spoofing via redirect (CVE-2020-15677). When recursing through layers while scrolling, an iterator may have become invalid, resulting in a potential use-after-free scenario (CVE-2020-15678). Note that Enigmail will no longer let you manage your PGP keys, but instead will only provide a migration tool. Thunderbird will no longer use the system keyring and GnuPG; instead, it will handle PGP keys internally. To use your existing PGP keys with Thunderbird 78 and above, you must use the migration tool from Enigmail upon the first Thunderbird run. See the migration notes on the Mageia wiki. Also note that, to protect your keys, you should define a master password in Thunderbird.