extra language support (XoopsX/xupdate#47)

Will check next dirs in archive.

legacy: `/extras/extra_languages/<LANG>/html`
          or
        `/extras/extra_languages/<LANG>`

Others: `extras/html/modules/language/<LANG>`
          and
        `extras/xoops_trust_path/modules/language/<LANG>`
Merge pull request #48 from XoopsX/extra_lang

extra language support (XoopsX/xupdate#47)