converts to UTF-8
tables used:
KOI8-r
CP1251
ISO-8859-5
tables are loaded from ./mappings and are taken from the unicode.org website
example usage, converts somefilename.txt from KOI8-r to UTF-8:
prog somefilename.txt 1
1: KOI8-r
2: ISO-8859-5
3: CP1251