[PATCH] fix building dictionaries when PERL_UNICODE environment

[Petr Vorel]

Hi,

I run into troubles while building dictionaries, because I have on my 
system set PERL_UNICODE=SDL (perl script 
clone/dictionaries/dictionaries/util/th_check.pl dies as it's forced to 
use UTF-8, but not all dictionaries are in this encoding).
Not sure whether it's good idea to handle it. If yes, there is a working 
solution (I'm sure, there must be better place to reset the variable).

Petr