[SOLVED] Firefox & Thunderbird's languages

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http://www.linuxquestions.org – I'd upgrade to Slackware64-14.0 and when I was with 13.1, I had the latest firefox and thunderbird installed by scripts, each one in my native language. But now I would like to use the official slackware's packages, and notice that they show up in english after I upgraded to slackware64-14.0. Does anyone knows the recommended way to change the languages (locales) for firefox and thunderbird (using the packages sent by slackwares's mirrors)? (HowTos)