Log Message:
Update to 31.4.0

Changelog:
Fixed The previous issues with jp mac builds have now been fixed, and \ 
Thunderbird will no longer need to be run in 32-bit mode.
Fixed Security fixes can be found here
Fixed Installing extensions within Thunderbird no longer requires download and \ 
installing as a file (Bug 1081190)
Fixed Autocomplete suggestion sort order was adjusted to prioritize entries \ 
where the search string matches the beginning of a word (Bug 970456)

Fixed in Thunderbird 31.4
    2015-04 Cookie injection through Proxy Authenticate responses
    2015-03 sendBeacon requests lack an Origin header
    2015-01 Miscellaneous memory safety hazards (rv:35.0 / rv:31.4)