Update to thunderbird-3.1.3.

* Several fixes to improve stability.
* Several fixes to the user interface.
* Several security fixes:
MFSA 2010-63 Information leak via XMLHttpRequest statusText
MFSA 2010-62 Copy-and-paste or drag-and-drop into designMode document allows XSS
MFSA 2010-61 UTF-7 XSS by overriding document charset using <object> type
            attribute
MFSA 2010-59 SJOW creates scope chains ending in outer object
MFSA 2010-58 Crash on Mac using fuzzed font in data: URL
MFSA 2010-57 Crash and remote code execution in normalizeDocument
MFSA 2010-56 Dangling pointer vulnerability in nsTreeContentView
MFSA 2010-55 XUL tree removal crash and remote code execution
MFSA 2010-54 Dangling pointer vulnerability in nsTreeSelection
MFSA 2010-53 Heap buffer overflow in nsTextFrameUtils::TransformText
MFSA 2010-52 Windows XP DLL loading vulnerability
MFSA 2010-51 Dangling pointer vulnerability using DOM plugin array
MFSA 2010-50 Frameset integer overflow vulnerability
MFSA 2010-49 Miscellaneous memory safety hazards (rv:1.9.2.9/ 1.9.1.12)

(tnn)