Update Translate.php

Translations shouldn't be cached if they contain dynamic vars (sprintf)

On productcomments, 
<li>{l s='%1$d out of %2$d people found this review useful.' sprintf=[$comment.total_useful, $comment.total_advice] mod='productcomments'}</li>
was always printing the same sentence
Merge pull request #564 from sylwit/patch-1

[*] CORE : Translations shouldn't be cached if they contain dynamic vars (sprintf) in Translate.php