towlower - convert a wide character to lowercase
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 towlower function returns the lowercase
equivalent of wc, or WEOF if wc is
ISO/ANSI C, UNIX98
The behaviour of towlower depends on the LC_CTYPE
category of the current locale.
This function is not very appropriate for dealing with
Unicode characters, because Unicode knows about three cases:
upper, lower and title case.