thunderbird: updated to 24.6.0, firefox: updated to 30.0

Hi Due to a botched commit message, our security notification system wont send out a mail to this list. So here is a "manual" notification. contrib/thunderbird was updated to 24.6.0. opt/firefox was updated to 30.0. Mozillas advisory pages for thunderbird and firefox are located here: http://www.mozilla.org/security/known-vulnerabilities/thunderbird.html http://www.mozilla.org/security/known-vulnerabilities/firefox.html Sorry for the mess. -- Fredrik Rinnestam