[GRASS-translations] once again file encoding

[Robert Nuske]

Hi Translators,

there was a discussion on the german grass list about weird display of german 
umlaute in some strings. 

We found out that the two "old" po-files (grassmods & grasslibs) are using the 
iso-encoding and the two "newer" ones (grasstcl & grasswxpy) use utf-8. The 
new po-files seem to produce "good looking" umlaute and the old ones mixed up 
stuff.

I guess we should do something, probably changing the encoding of two files. 
But which encoding shall we keep?

cheers,
  robert