mask.c: Handle command-line arguments given in UTF-8 when
internal encoding is some codepage.

$ ../run/john -stdout -mask=M[üö]ller
Using default input encoding: UTF-8
Press 'q' or Ctrl-C to abort, almost any other key for status
Müller
Möller
2p 0:00:00:00 100.00% (2014-09-29 23:16) 9.523p/s Möller