Issue #4388: On Mac OS X, decode command line arguments from UTF-8, instead of

Issue #4388: On Mac OS X, decode command line arguments from UTF-8, instead of
the locale encoding. If the LANG (and LC_ALL and LC_CTYPE) environment variable
is not set, the locale encoding is ISO-8859-1, whereas most programs (including
Python) expect UTF-8. Python already uses UTF-8 for the filesystem encoding and
to encode command line arguments on this OS.