MFH: r394369

• Update Thunderbird to 38.2.0

Changes: https://www.mozilla.org/thunderbird/38.2.0/releasenotes/
Security: https://vuxml.freebsd.org/freebsd/c66a5632-708a-4727-8236-d65b2d5b2739.html
Approved by: ports-secteam (feld)