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`towlower'--translate wide-characters to lower case

     #include <wctype.h>
     wint_t towlower(wint_t C);
`towlower' is a function which converts upper-case wide-characters to
lower case, leaving all other characters unchanged.
`towlower' returns the lower-case equivalent of C when it is a
upper-case wide-character, otherwise, it returns the input character.
`towlower' is C99.
   No supporting OS subroutines are required.