Ensure that distributed timezone abbreviation files are plain ASCII.

 Ensure that distributed timezone abbreviation files are plain ASCII.
 
 We had two occurrences of "Mitteleuropäische Zeit" in Europe.txt,
 though the corresponding entries in Default were spelled
 "Mitteleuropaeische Zeit".  Standardize on the latter spelling to
 avoid questions of which encoding to use.
 
 While here, correct a couple of other trivial inconsistencies between
 the Default file and the supposedly-matching entries in the *.txt
 files, as exposed by some checking with comm(1).  Also, add BDST to
 the Europe.txt file; it previously was only listed in Default.
 None of this has any direct functional effect.
 
 Per complaint from Christoph Berg.  As usual for timezone data patches,
 apply to all branches.
 
 Discussion: https://postgr.es/m/20200716100743.GE3534683@msg.df7cb.de