Update hsluv.* files from https://github.com/hsluv/hsluv-c

This only add a minor document update.

src/colorscheme/hsluv.h

@@ -79,6 +79,9 @@ void hpluv2rgb(double h, double s, double l, double* pr, double* pg, double* pb)
  * @param[out] ph Hue. Between 0.0 and 360.0.
  * @param[out] ps Saturation. Between 0.0 and 100.0.
  * @param[out] pl Lightness. Between 0.0 and 100.0.
+ *
+ * Note that HPLuv does not contain all the colors of RGB, so converting
+ * arbitrary RGB to it may generate invalid HPLuv colors.
  */
 void rgb2hpluv(double r, double g, double b, double* ph, double* ps, double* pl);