///
/// Generates cross-browser-compatible `box-shadow` for a given element.
///
/// @author drublic
///
/// @link http://caniuse.com/css-boxshadow caniuse
/// @link http://www.w3.org/TR/css3-background/#the-box-shadow spec
///
/// @param {List} $values
///
/// @output
/// ```css
///   -webkit-box-shadow: <values>;
///           box-shadow: <values>;
/// ```
///
/// @example
///   .selector {
///     @include x-box-shadow(5px 5px 10px 5px #aaa);
///   }
///
@mixin x-box-shadow ($values...) {
	-webkit-box-shadow: $values; // iOS Safari 3.2 - 4.3, Android 2.1+
	        box-shadow: $values;
}