Log Message:
Update thunderbird15 and thunderbird15-gtk1 to 1.5.0.12 (they skipped .11 to stay
on par with Firefox?).

Security fixes in this version:

MFSA 2007-15 Security Vulnerability in APOP Authentication
MFSA 2007-12 Crashes with evidence of memory corruption

For more info, see http://www.mozilla.com/en-US/thunderbird/releases/1.5.0.12.html