The towlower function is the wide-character equivalent of the
tolower function. If wc is a wide character, it is converted to
lowercase. Characters which do not have case are returned unchanged. If
wc is WEOF, WEOF is returned.
The behaviour of towlower depends on the LC_CTYPE category of the current
This function is not very appropriate for dealing with Unicode characters,
because Unicode knows about three cases: upper, lower and title case.