Update library/less/_mixins.less

Added .boxShadow(none) mixin

library/less/_mixins.less

@@ -198,10 +198,16 @@ BOX SHADOW
 *********************/
 
 /* .boxShadow(0,0,4px,0,#444); */
-.boxShadow(@x: 0, @y: 0, @radius: 4px, @spread: 0, @color: rgba(0,0,0,0.5)) {
+.boxShadow(@x: 0, @y: 0, @radius: 4px, @spread: 0, @color: rgba(0,0,0,0.5)) when (isnumber(@x)) {
 	-webkit-box-shadow: @x @y @radius @spread @color;
 	   -moz-box-shadow: @x @y @radius @spread @color;
-					box-shadow: @x @y @radius @spread @color; 
+			box-shadow: @x @y @radius @spread @color; 
+}
+/* .boxShadow(none); */
+.boxShadow(@x: none) when (iskeyword(@x)) {
+	-webkit-box-shadow: @x;
+	   -moz-box-shadow: @x;
+			box-shadow: @x; 
 }
 
 /*********************