towlower—translate wide characters to lowercase     #include <wctype.h>
     wint_t towlower(wint_t c);
     
   Description
towlower is a function which converts uppercase wide characters to
lowercase, leaving all other characters unchanged.
   
Returns
towlower returns the lowercase equivalent of c when it is a
uppercase wide character; otherwise, it returns the input character.
   Portability
towlower is C99.
   No supporting OS subroutines are required.