Updated thunderbird packages fix security vulnerability

Several flaws were found in the processing of malformed web content. A web page containing malicious content could cause Thunderbird to crash or, potentially, execute arbitrary code with the privileges of the user running Thunderbird (CVE-2016-1930, CVE-2016-1935). Multiple security flaws were found in the graphite2 font library bundled with Thunderbird. A web page containing malicious content could cause Thunderbird to crash or, potentially, execute arbitrary code with the privileges of the user running Thunderbird (CVE-2016-1521, CVE-2016-1522, CVE-2016-1523, CVE-2016-1526). Thunderbird includes a bundled copy of the graphite2 library, which has been updated in Thunderbird 38.6.0.