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