13.6.2.2 Unicode case insensitive string comparision

New functions lw:unicode-string-equal , lw:unicode-string-not-equal , lw:unicode-string-lessp , lw:unicode-string-not-lessp , lw:unicode-string-greaterp and lw:unicode-string-not-greaterp compare strings similarly to cl:string-equal etc, but using Unicode's simple case folding rules.